Body Temperature Measurement Devices, Methods, and Systems

ABSTRACT

A patient&#39;s body temperature measurement may be made by varying the heat transfer dynamics of a fluid exiting the patient&#39;s body and fitting parameters of heat transfer configuration to measurements under the varied conditions. Then the input temperature of the patient core can be extracted from the model and a current temperature measurement remote from the patient core and optionally other measurements such as fluid flow rate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.16/387,715, filed Apr. 18, 2019, which is a Continuation of U.S.application Ser. No. 15/766,766, filed Apr. 6, 2018, now U.S. Pat. No.10,668,206, which is a U.S. national stage filing under 35 U.S.C. § 371of International Application No. PCT/US2016/056198, filed Oct. 8, 2016,which claims the benefit of U.S. Provisional Application No. 62/239,838filed Oct. 9, 2015 and U.S. Provisional Application No. 62/268,511 filedDec. 17, 2015, all of which are incorporated herein by reference intheir entirety.

BACKGROUND

Extracorporeal blood treatments fall into a variety of categoriesranging from blood oxygenation and therapeutic hypothermia to renalreplacement therapies such as hemodialysis (HD). In extracorporeal bloodtreatments, such as HD, blood is pumped from a patient through a bloodcircuit and through a treatment device, such as a dialyzer. Toxins andelectrolyte exchange across a dialyzer membrane to exchange with atreatment fluid. The exchange causes the removal of waste products inthe blood and excess water. A substantial volume of the patient's bloodmay pass through an extracorporeal blood treatment system during thecourse of a treatment such that any heat transfer to or from the bloodcan upset the patient's body temperature. Systems are also known whichare used to detect patient's core temperature to permit the control ofthe return temperature of the blood to ensure the patient's bodytemperature is properly controlled.

SUMMARY

In a principal application, a patient's body temperature is calculatedresponsively to a temperature of blood flowing through a blood circuittaken at an extracorporeal blood treatment component. Blood flows intoan arterial line in extracorporeal blood circuit through one or moredevices such as a treatment device, and back to a patient. A system,device, or method may measure a blood inlet temperature, which may benear, in magnitude, to the patient's core temperature using a sensorthat is remote from the inlet. For example, the inlet may be at thepatient access. The inlet temperature may be calculated from thetemperature sensor indication in spite of a temperature change of theblood in the blood circuit due to heat gain or loss caused by heattransfer between the blood and the external environment of the bloodcircuit. For example, in a simple example, blood flows from a patientinto a tube which exchanges heat with the surrounding ambient air, theair being at a temperature below a core temperature of the patient. As aresult, the blood cools within the tube. If the heat transfer propertiesof the tube are known (that is the internal and external heat transfercoefficient, tube conductivity, and ambient temperature are known), theblood temperature can be inferred by calculation from a measurement ofthe blood at a point along the tube. This may be done by calculating theheat lost up to the point where the temperature is measured and therebydetermining the temperature at a point before the blood reached thetube. However, such information may not be available particularly thetemperature of the external environment. In addition, the latter mayvary along the length of the circuit from the inlet to the temperaturesensor.

Knowing the precise heat transfer conditions required to make such acalculation is difficult. This may be for a variety of reasons includingmanufacturing variability of the tube, variation in externaltemperature, imprecise values for heat transfer coefficients which areinfluenced by external forced convection as well as thermally-drivennatural convection, etc. According to the disclosed embodiments, thetemperature is measured at multiple flow rates and temperature readingsfor each condition are stored. Then these readings are used with athermal model of the system to calculate the inlet temperature. In anembodiment, the heat transfer rate is the same for two flow rateconditions. This gives two unknowns (the heat transfer rate) and twoequations allowing the inlet temperature to be calculated from theremote temperature readings and the flow rates, which are known. Inembodiments this initial estimate of the inlet temperature can beimproved by using an initial guess, estimate, or measurement of theambient temperature to recursively calculate an improved estimate of theinlet temperature which may be used again to improve it until converged.In other embodiments the unknown parameters of inlet temperature heattransfer rate (power units) may be calculated using a brute forceoptimization method such as an annealing algorithm or Monte Carlomethod. The latter may be preferred where the fluid temperature ismodeled as an exponential (decay), for example using log meantemperature difference (LMTD). In further embodiments, the ambienttemperature may be estimated by fitting three temperatures and threeflow rates as knowns to a thermal model of the flow system. From thedisclosure below, it should be evident that the principles and featuresof the disclosed subject matter may be applied to other fluid systemssuch as a pumped fluid system with a storage vessel, for example, or ablood system connected to a non-human animal.

In a method embodiment:

1. The temperature of blood flowing at a single point in the arterialline is measured after tracking for a steady state condition (i.e., zerochange over time) at a first flow rate, for example, maximum blood flowand the temperature recorded.

2. Then, the above is repeated but with the flow rate at another flowrate, for example, 50% of maximum blood flow. These flow rates areexamples and other flow rates can be used as long as they are different.

3. Next, assuming the heat transfer rate (power gain or loss) due totemperature differential between the fluid and ambient temperature isconstant (i.e., constant heat transfer rate) at both blood flow rates,the patient blood temperature (T_(p)) is calculated from bothtemperatures according to

${Tp} = \frac{{T_{c1}\mspace{11mu} F_{1}} - {T_{c2}\mspace{11mu} F_{2}}}{F_{1} - F_{2}}$

where T_(c1)=Temp reading for full blood flow, T_(c2)=Temp reading for50% blood flow, F₁=maximum flow rate, F₂=50% maximum flow rate. This isbased on a single heat transfer rate (power units) in the channel so therate of change in temperature is inversely proportional to the flowrate.

Instead of maximum flow rate or 50% flow rate, F₁ can be a known firstflow rate and F₂ can be a known second flow rate where the second flowrate is approximately 50% of the first flow rate or some other fractionor multiple thereof. Again, any combination of one or more flow ratesand any number of temperature measurements may be used to infer the coretemperature from a variety of different thermal models of a system.Indirect temperature measurements of the target fluid (e.g., blood) maybe made and used, for example, the temperature of spent dialysateleaving a dialyzer may be used instead of direct measurement of thetemperature of the blood if the flow rates allow the assumption that thedialysate is near equilibrium with the blood. The analytical ornumerical model to which the dialysate temperature is applied to inferthe core temperature may appropriately represent the known and unknownthermal parameters of the system to permit the core temperature to beinferred.

The above estimate of inlet temperature can be refined by calculating aratio of average temperature differences (blood and externaltemperature) based on a measured or estimated external temperature asdiscussed herein. The method can be further refined by using log meantemperature difference and even further refined by iterativelycalculating an external (ambient) temperature. The terms externaltemperature, environment temperature, and ambient temperature are usedinterchangeably herein. Also the inlet temperature and core temperatureeffectively refer to the same target temperature value that is sought tobe estimated using the disclosed subject matter.

It will be evident to those of skill in the art that the method employsan approximation of the heat loss that assumes the heat loss between thepatient and the temperature sensor is such that the change intemperature along the arterial line is low relative to the temperaturedifference between the patient blood temperature and the ambient. Inscenarios where that assumption does not apply, a suitable curve, suchas an exponential decay function, can be fitted to multiple measuredtemperatures for a larger number of flow rates. The log mean temperaturedifference may be used, for example.

The approximation of the above method provides the advantage ofrequiring only two samples. Further the use of maximum and half-maximumflow rates can be provided during a typical treatment. The maximum flowrate may be a maximum safe flow rate with a safety margin such that saidmaximum is a reasonable rate for actual treatment. In furtherembodiments, temperature can be sensed along multiple segments of thearterial line and a single curve or line fitted to the multipledisplaced segments. In each case, the fitted function may be used withknown configuration data such as a physical spacing between multipletemperature samples to extrapolate the temperature at the patient. Thismethod may not be as robust because it assumes the heat transfercharacteristics of the paths between temperature sensors is related, ina known way—for example identical—and one of the temperature sensors andthe inlet.

The method may be modified by providing other variables and basicassumptions about the flow system. For example, measurements oftemperature at multiple points along the length of a blood circuitportion may be provided. The temperatures of parts of the flow circuitmay be detected and used. Ambient temperature may also be used to refineestimates of the patient blood temperature. Alternately an ambienttemperature may be stored based on predefined data or may be input by anoperator to the controller or a standard value used.

According to embodiments, the temperature correction may be used todetect the core temperature of a patient, effectively correcting for theeffect of heat exchange in the tubing from the patient to thetemperature sensor. In embodiments, this corrected temperature is usedto determine an abnormal patient core temperature, for example due to aninflammatory process which could occur during a treatment. In otherembodiments, the corrected temperature may be used for negative feedbackcontrol of the return blood temperature to the patient.

Objects and advantages of embodiments of the disclosed subject matterwill become apparent from the following description when considered inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

Embodiments will hereinafter be described in detail below with referenceto the accompanying drawings, wherein like reference numerals representlike elements. The accompanying drawings have not necessarily been drawnto scale. Where applicable, some features may not be illustrated toassist in the description of underlying features.

FIG. 1 shows an extracorporeal blood processing machine with a bloodcircuit and other components for completing a blood temperaturemeasurement and performing a blood treatment.

FIG. 2 illustrates an embodiment of a heat transfer model, according toembodiments of the disclosed subject matter.

FIG. 3A shows a graph of blood temperature versus displacement of bloodalong a flow channel, according to embodiments of the disclosed subjectmatter.

FIGS. 3B and 3C are flow charts showing respective methods that can beimplemented by a treatment machine controller, for example, to estimatepatient core temperature from a temperature measurement remote from apatient or other subject.

FIGS. 3D and 3E show a result of a simulation of the method of FIGS. 3Cand 3D, respectively.

FIG. 4 shows a method of determining and employing blood temperature fordetecting a patient condition, according to embodiments of the disclosedsubject matter.

FIG. 5 shows an extracorporeal blood processing machine with a bloodcircuit and other components for completing a blood temperaturemeasurement and performing a blood treatment with temperature regulationof return blood, according to embodiments of the disclosed subjectmatter.

FIG. 6 shows a method applicable to the embodiment of FIG. 5, accordingto embodiments of the disclosed subject matter.

FIG. 7 shows a graph of blood temperature versus displacement of bloodalong a flow channel, according to embodiments of the disclosed subjectmatter.

FIG. 8 shows a flowchart of a temperature measurement process thatoccurs during a temperature measurement phase of a startup mode of ablood treatment device such as a dialysis system.

FIG. 9 illustrates an active temperature control mechanism forregulating body temperature of a subject based on the temperature ofblood from the patient and optionally based on the temperature of theblood returned to the patient as well.

FIG. 10 illustrates a method of active temperature regulation using thedisclosed temperature measurement embodiments.

FIGS. 11A and 11B show results of simulations of a refined method basedon that of FIGS. 3C and 3D which increase accuracy by optimizing anestimate of the temperature of the environment around a blood circuit.

FIG. 12A shows an example of a variable environment temperature versuslength to describe features of the temperature determinationembodiments.

FIG. 12B shows the convergence of the core temperature estimate based onthe profile of FIG. 12A.

FIG. 13 shows a schematic of a dialysis system with various optionalcomponents for measuring temperature.

FIGS. 14A-14C show sets of control conditions for measuring coretemperature using the embodiments of FIG. 13 according to respectiveembodiments.

FIG. 14D represents adiabatic regulation for return blood temperatureidentical to patient blood temperature as measured according to theembodiments.

FIGS. 15A-15C are flow charts showing procedures for calculating patientcore temperature according to respective embodiments of the disclosedsubject matter.

FIGS. 16A through 16C show simulations corresponding to the methods ofFIGS. 15A through 15C.

DETAILED DESCRIPTION

Temperature measurement devices, methods, and systems for estimating apatient's core temperature from a temperature indicated at a point in ablood circuit remote from the patient's core may be employed in any typeof blood circuit, including platelet extraction, therapeutichypothermia, transfusion, blood oxygenation, renal replacement therapyor any type of extracorporeal blood treatment system. It will be evidentthat the methods, devices, and systems are applicable to any system inwhich a fluid, previously at equilibrium temperature with a patient'score, is drawn from a patient's body. Examples of fluid other than bloodmay include peritoneal dialysate, urine, or ultrafiltrate from animplanted artificial kidney.

Referring to FIG. 1, an extracorporeal blood treatment system 99includes a blood treatment system 99 that includes an extracorporealblood processing machine 102 that engages a blood circuit 98. The bloodcircuit 98 has an arterial blood line 112 and a venous blood line 111.The former is used to convey blood from a patient 106 via a patientaccess 108. The latter is used to return blood that has been treated bythe extracorporeal blood processing machine 102 back to the patient 106via the patient access 108. The blood circuit 98 transfers blood betweenthe patient and the extracorporeal blood processing machine 102 asindicated figuratively by fluid connections 126 and 128. Note thatportions of the blood circuit may reside within the extracorporeal bloodprocessing machine 102. The connections 126 and 128 may transfer bloodto and from a dialyzer, oxygenator, adsorbent, or some other componentor components of the extracorporeal blood processing machine 102 therebyto perform a treatment. A blood pump 118 may engage the blood circuit 98to pump blood therethrough. The blood circuit 98 may be a replaceabledisposable component. One or more temperature sensors 114, 116, 120,122, 124 may be arranged to measure a temperature of the blood atrespective points along the blood circuit 98. A controller 100 has auser interface 104. The controller receives temperature signals from theone or more temperature sensors and controls the pump 118. Inembodiments, the flow rate of blood may be directly measured by a flowsensor 117. The direct flow measurements may be applied in thecalculation of patient core temperature as discussed below.

In embodiments, a single temperature sensor is located at theextracorporeal blood processing machine 102 in the arterial line, forexample as indicate at 114 or 116. In other embodiments multiple sensorsmay be used, each at different positions along the blood line. Forpurposes of the discussion immediately below, an embodiment using asingle temperature sensor 116 will be described. The temperature sensor116 may be of a type that measure blood temperature by providing atemperature sensor in contact with the outside of a flow channel thatforms part of the blood circuit 98 arterial line 112. The temperaturesensor 116 may further be of a type that actively detects and controlsto minimize a flux of heat between the contents of the flow channel andthe external sensor through negative feedback control. This type oftemperature sensor, an active temperature sensor, is described ininternational patent application published as WO2014018798 to Newell.

In some embodiments employing the external sensor described in theabove-cited international patent publication, a temperature sensor isincluded with a vessel/channel that has a temperature detecting device.A first temperature sensor can be attached to or placed against a wallof a vessel/channel and is configured for carrying or containing afluid. A second temperature sensor can be separated from the firsttemperature sensor by an insulating body having a thermal resistancesimilar to the vessel/channel wall. There can be a temperatureregulating device in thermal contact with the second temperature sensorand configured to receive first and second temperature indicationsignals, respectively, from the first and second temperature sensors.The temperature regulating device can be further configured to minimizea difference in temperatures indicated by the first and secondtemperature signals by regulating a rate of flow of heat between thefirst and second temperature sensors to prevent a flow of heat betweenthe fluid (in this case, blood) and one or both temperature sensors. Theregulating device may include an electrical resistance heater.

The active temperature sensor described above is one type of temperaturesensor that produces very accurate measurements of fluid temperature. Aproblem with these types of sensors is that they are not practical tolocate close to the patient and therefore temperatures measured withthem may be biased due to transfer of heat from the fluid circuitleading from the patient or other subject to the sensor. The disclosedembodiments estimate a correction for this bias permitting an accuratemeasurement of core temperature to be obtained. The blood circuit 98 mayinevitably transfer heat from the environment to or from the bloodflowing through it. This may cause a difference between the bloodtemperature leaving the patient 106 and the blood temperature measuredat the temperature sensor 116. This may be mitigated by providing atemperature sensor right at the patient 106 access 108, however forprecise temperature measurement as in the active temperature sensor 116describe above, for practical reasons that should be apparent, it isdifficult or costly to provide a disposable blood circuit 98 that cansupport the active temperature measurement configuration. This type ofsensor is much more suitably provided on the extracorporeal bloodprocessing machine 102. As a result, there will be a length of flowchannel (typically tubing) leading from the patient 106 access 108 tothe temperature sensor 116. Referring to FIG. 2, heat transfer to thesurrounding environment 204, such as the ambient air, between the blood204 carried in the length of arterial line 112 upstream of thetemperature sensor 116 results in a difference across a thermalresistance which creates a difference in the temperature of bloodleaving the patient 106 and the temperature measured at the temperaturesensor 116.

In a principal application, a patient's body temperature is calculatedresponsively to a temperature of blood flowing through a blood circuittaken at an extracorporeal blood treatment component. Blood flows froman arterial line in extracorporeal blood circuits. The disclosed subjectmatter may compensate for a temperature change in the arterial line dueto heat gain or loss depending on temperature difference and, optionallyother factors, between the fluid circuit environment and the bloodflowing in the arterial line. The resulting compensation, which may begenerated computationally with a processor, may then be used tocalculate a core temperature as indicated by the temperature of theblood leaving the patient's body. It should be evident that theprinciples and features of the disclosed subject matter may be appliedto other fluid systems such as a pumped fluid system with a storagevessel, for example, or a blood system connected to a non-human animal.

In a method employing a linear extrapolation of the blood temperatureleaving the patient 106:

-   -   1. The temperature of blood flowing at temperature sensor 116 in        the arterial line 112 is measured after tracking for a steady        state condition (i.e., zero change over time) at maximum blood        flow and the temperature recorded. The controller 100 may        automatically control the blood pump 118 to effect the desired        blood flow. The blood flow rate may be determined by the        controller according to parameters entered in the user interface        104.    -   2. The operation 1, above, is repeated but with the flow rate at        50% of maximum blood flow which may also be selected by the        controller 100. Other percentages than 50% may be employed as        well.    -   3. Next, the controller 100 calculates the patient blood        temperature (T_(p)) from both temperatures according to

$\begin{matrix}{{Tp} = \frac{{T_{c\; 1}\; F_{1}} - {T_{c2}\; F_{2}}}{F_{1} - F_{2}}} & (1)\end{matrix}$

where T_(c1)=Temp reading for full blood flow, T_(c2)=Temp reading for50% blood flow, F₁=maximum flow rate, F₂=50% maximum flow rate. Thisassumes a single heat transfer rate (power units) in the channel so therate of change in temperature is inversely proportional to the flowrate. In alternative embodiments, a curvilinear extrapolation of theblood temperature at the patient 106 may be used.

Instead of maximum flow rate or 50% flow rate, F₁ can be a known firstflow rate and F₂ can be a known second flow rate where the second flowrate is approximately 50% of the first flow rate.

Using the above-described method, a temperature loss/gain can beestimated for an extracorporeal blood treatment. A first temperature ata first flow rate can be measured at a temperature sensor. A secondtemperature at a second flow rate can be measured at the temperaturesensor. A patient blood temperature can be found based on the first andsecond temperatures and first and second flow rates. The patient bloodtemperature can be compared to a third temperature at a third flow rate,where the third flow rate can be a normal flow rate of the machine forthe particular patient or for a particular treatment. Temperature gainor loss can be used to estimate a corresponding temperature loss or gainat a fluid temperature regulator. As further described below,temperature gain or loss can further be estimated for the return part ofthe blood circuit between the temperature sensor and the patient. Theestimated temperature gain or loss for the return part of the bloodcircuit can be used by a fluid temperature regulator to heat or cool thefluid by an amount determined to counteract the gain or loss of thecircuit, i.e., heat or cool the fluid to by a temperature equal to thesum of the temperature loss or gain estimated for the supply of theblood circuit to the temperature sensor and the temperature loss of gainestimated for the return of the blood circuit from the temperaturesensor to the patient. In addition, the temperature of return blood maybe reduced to by a predefined temperature interval to help control afever. The return temperatures for given fever levels may be stored by asystem controller and used to control a heating apparatus that controlsthe temperature of blood returned to the patient.

Referring to FIG. 3A, a graph illustrates how the temperature of theblood may decay exponentially (dashed lines) as it is displaced alongthe length of arterial line 112 between the access 108 and thetemperature sensor 116. The two curves illustrate how the decay rate isfaster at a low flow rate compared to a higher flow rate. T_(p) is anextrapolated temperature of the blood leaving the patient generated byextrapolation according to respective embodiments. The extrapolation maybe done by various means as discussed below. In embodiments in which alinear extrapolation of the blood temperature leaving the patient isperformed, temperature may be measured at a single point along thearterial line. In other embodiments, the temperature measurement may bemade at multiple points (not illustrated here). A curvilinearextrapolation or a model of the heat transfer that takes account of theexponential decay may be used. A non-exponential model may also be usedsuch as an arbitrary fittable function such as a polynomial function. Inembodiments, the function is selected to model the thermal behavior ofthe system such as an exponential decay function which represents amodel of the transfer of uniform heat from or to a tube with a flow anduniform heat transfer U-value (W/m²K) along the tube. The dotted linesshow the exponential decay of the temperature assuming the ambienttemperature T_(a) outside the arterial line 112 is lower than the bloodtemperature. The graph also illustrates that the temperature change ofblood from the point where it leaves the patient at temperature T_(p)and the point or points where it is measured (intermediate points Td1,Td2) T_(c1), T_(c2). The temperature change may be a minor fraction ofthe temperature difference between the blood temperature and the ambienttemperature T_(a) so that the approximation of equation 1 holds. Thelatter condition makes the linear approximation described abovereasonable and allows two temperature measurements at two flow rates tobe used to extrapolate a very accurate temperature estimate for bloodleaving the patient. An exponential model that may be fit to severaltemperature data points is:

$\begin{matrix}{T_{c} = {T_{a} + {\left( {T_{p} - T_{a}} \right)\mspace{11mu}{e\;\left\lbrack {- \frac{x_{L^{L}}}{Q}} \right\rbrack}}}} & (2)\end{matrix}$

Where T_(c) is a temperature of the fluid measured at position Ldistance from the input fluid at temperature T_(p), Q is the flow rate,T_(a) is the ambient temperature, and X_(L) is a lumpparameter=UC/c_(p)ρ where U is an overall U-value that accounts for heattransfer resistance, C is the circumference of the tube taken at theradius upon which the U-value is derived, and c_(p)ρ is the product ofthe fluid specific heat and density. The exponential may be fitted tosolve for T_(a) and X_(L) using multiple temperatures at multipledistances along the tube, multiple flow rates, or a combination. Thetemperatures may be oversampled and applied to regression. Multipletemperatures will be of limited use in the context of blood temperaturemeasurement because the heat transfer properties (outside temperature,adventitious insulation or heat sources such as caused by contact withperson or bed, etc.) of the respective circuit portions between thetemperature sensors are likely to be different and unpredictable.

Referring to FIG. 3B, the estimate given by equation 1 can be improvedby using the estimate for the patient temperature T_(p) S10 fromequation 1 or similar calculation as discussed elsewhere and anestimate, or approximation, of the ambient temperature S12 to calculatetemperature difference parameters S14 for the flow at each flow rate. Inaddition, alternatively, the initial calculation of T_(p) can be skippedand a standard value used instead. Using these temperature parameters,the ratios of the rate of heat loss for the flows at the two flow ratescan used to solve for a new estimate of the patient core temperatureS16. See equation 3a where TDPi represents a temperature parameter forthe flow rate i. An example of a temperature difference parameters isthe average of the core and measured temperatures minus the ambienttemperature estimate (T_(bi) as given by equation 3b) may be used.

$\begin{matrix}{T_{p} = \frac{{T_{c1}F_{1}} - {\left( \frac{TDP_{1}}{TDP_{2}} \right)\mspace{11mu} T_{c2}F_{2}}}{F_{1} - {\left( \frac{{TDP}_{1_{1}}}{{TDP}_{2}} \right)F_{2}}}} & \left( {3a} \right) \\{T_{bi} = {\frac{\left( {T_{p} + T_{ci}} \right)}{2} - T_{a}}} & \left( {3b} \right) \\{T_{p} = \frac{{T_{c1}\mspace{11mu} F_{1}} - {\left( \frac{T_{b1}}{T_{b2}} \right)\mspace{11mu} T_{c2}\mspace{11mu} F_{2}}}{F_{1} - {\left( \frac{T_{b1}}{T_{b2}} \right)\mspace{11mu} F_{2}}}} & \left( {3c} \right)\end{matrix}$

The recalculated core temperature T_(p) can then be used to derive a newestimate of the temperature difference parameters S18 and the coretemperature recalculated. For example, if the average temperaturedifference (T_(bi)) is used this would be plugged into equation 3a togive the updated T_(p) as in equation 3c. The update can be iterateduntil T_(p) converges S20 or for a fixed number of iterations. Othertermination conditions can also be used such as a variable number ofiterations that corresponds to the difference in the flow rates F₁ andF₂.

Referring to FIG. 3C, a particular example employs the log meantemperature difference (LMTD) which is a temperature difference based onthe assumption of the exponential decay of temperature in a tubecarrying a fluid. It will be understood that the ratio of the F₁ flowrate multiplied by the temperature change of the blood from the patientto the temperature sensor to the corresponding temperature change at theF₂ flow rate multiplied by that flow rate is equal to the ratio of LMTDsat the corresponding flow rates. That is:

$\begin{matrix}{\frac{LMTD_{1}}{LMTD_{2}} = \frac{\left( {T_{p} - T_{c1}} \right)\mspace{11mu} F_{1}}{\left( {T_{p} - T_{c2}} \right)\mspace{11mu} F_{2}}} & \left( {3d} \right)\end{matrix}$

where LMTD is given by:

$\begin{matrix}{{LMTD} = \frac{\left( {T_{p} - T_{a}} \right) - \left( {T_{ci} - T_{a}} \right)}{{\ln\mspace{11mu}\left( {T_{p} - T_{a}} \right)} - \left( {T_{ci} - T_{a}} \right)}} & \left( {3e} \right)\end{matrix}$

Where T_(a) is an estimate for the ambient temperature and T_(ci) is themeasured value for the flow rate I (=1 or 2). The ambient temperatureT_(a) can be directly measured or a standard value used. If an estimateor measurement of the ambient temperature T_(a) and an initial estimatefor T_(p) from equation 1 (S21) are plugged into equation 3 (S24), thenequation 4, which is equation 3 rearranged, can be used to solve for animproved estimate of T_(p) S26. Then the LMTD ratio can be solved againS28 and this process iterated using increasingly better estimates ofT_(p) until it converges S30 or a fixed number of iterations is carriedout.

$\begin{matrix}{{Tp} = \frac{T_{c\; 1} - {\left( \frac{LMTD_{1}}{LMTD_{2}} \right)\mspace{11mu} T_{c\; 2}F_{2}}}{F_{1} - {\left( \frac{LMTD_{1}}{LMTD_{2}} \right)\mspace{11mu} F_{2}}}} & (4)\end{matrix}$

FIG. 3D shows the results of using the estimation procedure of FIG. 3Bwith a simulated fluid flow calculated from a patient temperature of 40and flow rates of 100 and 200 ml/min and T_(c1) and T_(c2) of 36.5 C and33.8 C, respectively. A constant UA and L were used. The results showthat T_(p) converged within 4 iterations to a value that is close to theground truth value of 40. FIG. 3D shows the results of using theestimation procedure of FIG. 3C with a simulated fluid flow calculatedfrom a patient temperature of 40 and flow rates of 100 and 200 ml/minand T_(c1) and T_(c2) of 36.5 C and 33.8 C, respectively. A constant UAand L were used. The results show that T_(p) converged within 4iterations to a value that is close to the ground truth value of 40.

Referring to FIG. 4, according to a method, a treatment process isunderway at S1 in which blood is circulated from a patient through ablood treatment system and back to the patient as described, forexample, with reference to FIG. 1. At a time selected by a controller,at S2, a test interval is initiated which begins by establishing apredefined first flow rate of the blood. The flow rate is established atS3. To ensure the heat transfer reaches a near-steady state condition, awatchdog timer may be initialized at S4. Alternatively, or in addition,the temperature (e.g., at 116) may be sampled (S5) by the controllerwhich may wait for a constant or near-constant (unchanging over timewithin a predefined temperature interval stored by the controller)temperature at the sensor (e.g., 116). If the temperature variation isoutside a predefined range, for example it fails to settle to a steadystate, this may be detected at S6 by comparing the profile establishedby the samples recorded at S5 to a predefined requirement stored in thecontroller and a user interface message output at S7 with reversion toS4. If the temperature profile is satisfactory at S6, a temperature isrecorded (or the latest one or more samples recorded) at S8. At S9, asecond predefined flow rate is established. Again, to ensure the heattransfer reaches a near-steady state condition, a watchdog timer may beinitialized at S10. Alternatively, or in addition, the temperature(e.g., at 116) may be sampled (S11) by the controller which may wait fora constant or near-constant (unchanging over time within a predefinedtemperature interval stored by the controller) temperature at the sensor(e.g., 116). If the temperature variation is outside a predefined range,for example it fails to settle to a steady state, this may be detectedat S13 by comparing the profile established by the samples recorded atS11 to a predefined requirement stored in the controller and a userinterface message output at S12 with reversion to S10. If thetemperature profile is satisfactory at S13, a temperature is recorded(or the latest one or more samples recorded) at S14. The controller thencalculates, at S20, a blood temperature leaving the patient, forexample, using the linear extrapolation indicated above. The temperaturemay be output through a user interface S21. The temperature may becompared to a time profile or predefined temperature to determine ifthere is an abnormal condition such as a fever at S22 and if so, thecondition detected may also be output at the user interface at S23.Control returns to S1.

A modification of the method of FIG. 4, which may be used with any ofthe embodiments, is to add a sequence in which the first flow rate isreestablished and the temperature reading performed again. Thisadditional temperature reading may be used to confirm that the steadystate conditions existed since the first measurement at the first flowrate and thereby confirm that the temperatures at the first and secondflow rates are valid. Also, if any drift in the heat transfer conditionsbetween the two first flow temperature measurements is linear, thentaking an average of the two first flow temperature measurements wouldbe representative of the conditions at the time the second temperaturemeasurement was made. So, if T_(c3) is the third temperature measurementat F₁, in the equations presented herein, T_(c1) is simply replaced withan average of T_(c1) and T_(c3) in the new embodiments.

The core temperature data may be recorded in a treatment log andconnected to a patient profile. The core temperature data may berecorded as a temperature vs. time log profile for each treatment. Theprofile over many treatments may be used as a reference in order toidentify an abnormal profile for the patient. The temperature data maybe stored by a treatment machine controller (remotely or locally) andused to output an indication that an abnormal condition exists bycomparing standardized normal profile range with a current profileduring a treatment.

FIG. 5 shows a system that is mostly identical to that of FIG. 1 exceptthat is shows a temperature regulation effecter 140 which adds heat tothe blood prior to returning the blood to the patient 106. Inembodiments, the temperature regulation effecter 140 may be a fluidwarmer that is controlled to regulate the temperature of returning bloodto a target temperature as indicated by a temperature sensor monitoringthe temperature of blood in the venous line 111. In embodiments of adialysis system, this temperature regulation may be done by warming thedialysate prior to contacting the dialyzer where it warms the blood. Inalternative embodiments, other methods and devices for warming blood,alone or in combination, may be employed to add heat to the blood or thepatient's body directly or indirectly. A blood warmer may be employed,preferably one with low current loss such as an infrared radiant heaterwith electrical field isolation. In other embodiments, a convectivewarmer such as one that separates an electrical heat source from bloodby circulating an intermediate heat transfer fluid between a bloodcircuit and a heater, for example, air or oil. A heating pad applied toa part of the patient with good circulation such as the thighs, abdomenor neck or any other suitable body part may also be used. In manyembodiments, the manner of providing heat to the blood or the body canbe of any suitable form.

FIG. 6 shows a method for regulating the return blood temperature. Atarget temperature is stored by a controller (e.g., 100). The target isused to regulate the return blood temperature at S40 for example bynegative feedback (using venous line temperature sensor) control of thevenous line temperature. The patient blood temperature is obtainedaccording to any of the methods described above through extrapolation atS42 and used to update the stored target at S44. This updated target isthen used for regulation of the return blood temperature. The target maybe extrapolated backwards using the temperature difference betweenarterial temperature at 116 and the extrapolated temperature such thatthe target is set equal to that difference added to the extrapolatedtemperature of the blood leaving the patient. This would fit thecircumstance of heat loss in the venous line being equal to the heatloss in the arterial line, both between the patient the respectivetemperature sensor. In addition, the same method will apply when thepatient target core temperature to be achieved is above or below acurrent temperature or normal temperature (forced body temperature)through the net withdrawal of heat or net supply of heat. The targettemperature may be a therapeutic temperature as for some types ofprocedures such as surgical procedures or treatment of injuries wherethe body temperature is lowered or raised (e.g., concussion treatment).In addition to the forced body temperature approach described above, themethod of FIG. 4 may be implemented to determine whether a fever existsprior to forcing the temperature or at intermediate points fordiagnostic purposes.

A problem with core temperature measurement in certain systems such asextracorporeal blood circuits is that such systems often need to heatblood of a patient to desired return temperature upon reinfusion to keepthe temperature of the patent at a desired level. To do this, heat maybe transferred to the returning blood, which is generally cooled bypassing through the treatment system. Of course a problem with this isthat the active temperature regulation system that accomplishes thisfunction of returning blood at a desired temperature will disrupt thenatural temperature of the patient and prevent the temperaturemeasurement process described herein from being diagnostically useful.

One device for mitigating the above problem is to measure the patient'stemperature, using the presently-disclosed methods, devices, andsystems, immediately after the first blood is drawn and before thepatient's body temperature is affected by the temperature controlsystem. See FIG. 8 and attending discussion for description of anembodiment. Another device for compensating the above problem is tomonitor core temperature continuously and to detect a change in bloodtemperature that might be a diagnostic indication such as a patientfever. In the latter method, the controller may trigger a diagnosticsignal upon detecting a predefined rate of change of core temperature ata time that blood return temperature and flow rate are held constant andblood outlet temperature remained steady for a predefined period of timeindicating a change in the patient's temperature homeostasis set-point.Others are described with reference to FIGS. 13 and 14A-14C.

FIG. 8 shows a flowchart of a temperature measurement process thatoccurs during a temperature measurement phase of a startup mode of ablood treatment device such as a dialysis system. The process isapplicable to a system such as a dialysis system where there is a bloodcircuit that interfaces with a treatment fluid circuit to transfer heattherebetween through a treatment device such as a dialyzer. A startupmode includes a priming procedure during which the treatment fluid andblood circuits are primed S30. A variety of procedures are known forfilling and optionally flushing blood and treatment fluid circuits andthe details are not relevant here.

At S32, if necessary depending on the priming procedure used, thetreatment fluid circuit is connected to a source of treatment fluid. Forexample, a dialysate circuit may be connected to a dialysate source. AtS34 the treatment fluid is flushed through the treatment device whileregulating its temperature by controlling a temperature regulator suchas a heater. A flow is established through the treatment device (e.g.,dialyzer) until the treatment fluid compartment is at a predefinedtemperature. The temperature may be, for example, a normal bodytemperature representative of the temperature of an afebrile subject.The treatment fluid is flushed at a sufficient rate in combination witha sufficient period of time (or total volume) such that the fluidcompartment is estimated to be at the constant predefined temperaturethroughout. The time and rate may be predetermined, for example, asufficient volume may be flushed at the predefined temperature todisplace the internal treatment fluid compartment volume three timesover. After this has been done, determined at S36, the treatment fluidpump is halted and a no-flow condition is established in the treatmentfluid circuit compartment S38.

At S40, the blood pump operates to establish the first flow rate (F₁)for temperature measurement. This is done for a sufficient time S42 toreach a steady state heat transfer condition. The temperature indicatedby the temperature sensor (T_(c1)) is recorded. At S44, the blood pumpoperates to establish the second flow rate (F₂) for temperaturemeasurement. This is done for a sufficient time S46 to reach a steadystate heat transfer condition. The temperature indicated by thetemperature sensor (T_(c2)) is recorded. Then the controller calculatesthe temperature from the two temperature readings and the flow ratesS248 as described herein according to any of the embodiments. Theprocess may be done with multiple flow rates and temperature readingseven though the conditions may be considered to be oversampled and anaverage of the estimations at the multiple combinations of flows andtemperature readings may be taken as a best estimate of the coretemperature.

FIG. 9 illustrates an active temperature control mechanism forregulating body temperature of a subject based on the temperature ofblood from the patient and optionally based on the temperature of theblood returned to the patient 201 as well. A treatment system with atreatment device 208, a controller 202, and a temperature regulator 205.The system may be as described with reference to FIG. 5. The controllerreceives venous and arterial temperature signals from respectivetemperature sensors 205 and 204. The temperature sensors 205 and 204 areconfigured to indicate the temperature of blood in venous 215 andarterial 214 lines of a blood circuit 216 and to perform feedbackcontrol of the temperature regulator (e.g., a dialysate heater orheater/cooler, for example) to regulate the patient's 201 bodytemperature during a treatment. FIG. 10 illustrates a method of activetemperature regulation using the disclosed temperature measurementembodiments in the system of FIG. 9 feedback control using thetemperature indicated by sensor 205, 204 or a combination thereof. Asdiscussed above and here, the core temperature is estimated tocompensate for heat loss in the blood circuit connecting the patient andthe temperature sensor and used as a control variable. The temperaturedifference between the core temperature as calculated using thedisclosed embodiments and the temperature indicated by the temperaturesensor 204 can be stored and used to estimate the core temperature afterthe temperature measurement at the multiple flow rates is performed, forexample after the temperature measurement phase of the startupprocedure. The temperature drop (or rise) may be store and applied as afixed value DT which assumes that the net change in temperature remainsconstant.

Tp=DT+Tci  (5)

Instead, the LMTD can be calculated from the temperature measurementprocedure and used with the estimated ambient temperature T_(a) and thetemperature from the sensor 204, T_(c), to calculate a lump parameter X

$\begin{matrix}{X = {\frac{UA}{Q\rho c_{p}} = {\frac{Q}{LMTD}\mspace{11mu}\left( {T_{p} - T_{c}} \right)}}} & (6)\end{matrix}$

where A is the heat transfer area of the blood circuit between thepatient and the temperature sensor, Q is the volume flow rate of blood(here, at the time of calculating X), T_(c) can be either T_(c1) orT_(c2), and the other parameters are as defined above. T_(p) can becalculated from equation 7 based on the current temperature T_(c) fromsensor 204.

$\begin{matrix}{T_{p} = {T_{c} + {X\mspace{11mu}\frac{LMTD}{F}}}} & (7)\end{matrix}$

Where LMTD is calculated from equation 3e based on a current temperatureT_(c), estimated ambient temperature, and a current flow rate F. Asshould be clear from the current description, other temperaturedifference parameters may also be used rather than LMTD. For example, aconstant average blood temperature of the blood circuit may be assumedrather than an exponentially changing temperature as assumed in usingLMTD. Thus, the core temperature may be calculated at S54 and atemperature differential or parameter such as X (equation 6) may bederived and stored at S56 and thereafter used to calculate the coretemperature at S58. At S50, the system 205 treats a patient 201 whileregulating the venous temperature responsively to the temperature 204using a final negative feedback control of the temperature regulator 207targeting a set-point of a return temperature indicated by 205, wherethe set-point is the controlled variable of the outer negative feedbackcontrol based on the core temperature. Meanwhile the temperatureindicated by sensor 204 is monitored and if a temperature vs timeprofile occurs that indicates that the heat transfer characteristic ofthe arterial line 214 between the sensor 204 has changed (disruption ofsteady state, “SS”), then at S60, the active temperature regulation maybe halted and the core temperature acquired again according to themethods and devices described herein. Note that S60 may form a separatethread that interrupts a loop going from S50 to S58 rather than asillustrated so that the temperature is monitored for a heat transfercharacteristic change continuously or at least frequently. Theindication of a disruption of steady state may be indicated by a rate ofchange of temperature that is high enough to make it unlikely to be dueto a change in the patient's body temperature. Mechanical disturbance ofthe blood circuit may be detected, for example by an accelerometertension sensor connected between the blood processing system supportingthe temperature sensor and the arterial portion of the blood circuit. Orthe accelerometer may be on the blood circuit. These and other means maybe provided to detect and indicate a disturbance or mechanical movementof the blood circuit. Other inputs such as video feed of the patient maybe used to determine if there is a possible disruption. For example, avideo of the patient which shows the patient shifting body position mayindicate a significant change such as the arterial line being moved orcovered by the patient's body.

The above methods rely on an estimate for the ambient temperature. Theprecise ambient temperature may not be known and the heat transferenvironment of the blood circuit may not correspond well to a singlemeasure of ambient temperature. For example, for a long arterial lineconnected between a treatment machine and a patient, parts of the linemay be lying on a bed which is slightly warmer than the roomtemperature, parts of the room may be cooler than other parts due todrafts or even the presence of occupants in the room. An effectiveambient temperature may produce greater accuracy. To estimate thisadditional unknown, the Tc for another flow rate F₃ may be used.Initially the estimate of ambient temperature T_(a) is used to calculatean estimate for X according to equation 6 using T_(c1) and F₁ or F₂ andT_(c2). The latter, rearranged to place T_(a) in terms of X calculatedfrom LMTD using the core temperature measurement based on T_(c3) and F₃,is:

$\begin{matrix}{T_{a} = \frac{{T_{c\; 3}e^{\frac{X}{F_{3}}}} - T_{p}}{e^{\frac{X}{F_{3}}} - 1}} & (8)\end{matrix}$

This value can be used for each iteration to update the estimate ofT_(p), then to update X and then to calculate a new T_(a) and so onuntil the values of T_(a) and T_(p) converge.

FIGS. 11A and 11B show how T_(p) converges using initial estimates ofT_(a) of 30 and 20, respectively with a correct constant value of 25. Totest the situation where T_(a) varies along the length of the bloodchannel between the patient and the temperature sensor, a varying T_(a)was used to generate the simulation as shown in FIG. 12A. A model wasgenerated that varied the simulated temperature surrounding a simulatedfluid channel around ±10. This tested the calculation of an effectiveambient temperature by iteration as described. The average value ofT_(a) along the length was 26.1. The value of T_(a) after convergenceusing the procedure outlined above was 25.5. Tests of various profilesthat T_(p) converged to the correct value even for a variety oftemperature variation profiles of the ambient temperature along thelength of the blood circuit. FIG. 12B shows the convergence of the coretemperature estimate based on the profile of FIG. 12A.

FIG. 13 shows a schematic of a dialysis system with various optionalcomponents for measuring temperature. A dialyzer 302 receives dialysateat a temperature TD_(i) indicated by temperature sensor 304 from adialysate supply line 340. The temperature of the dialyzer is indicatedas TD. Spent dialysate emerges through a dialysate outlet 432 at atemperature TD_(o) indicated by a temperature sensor 306. Blood entersthe filter from a patient access 309 and flows through an arterial line350. Blood initially enters at a temperature T_(p) which may beindicated by a temperature sensor proximate the patient 318 but is,according to the disclosed embodiments calculated from a temperature Tclocated remote from the patient access and indicated by a sensor 316.Heat exchanged with the external environment by the arterial line 350occurs at a rate which may be represented by a lump parameter X_(a). Thetemperature sensor 316 may be located at a treatment machine (not shownexcept for the components illustrated) measures temperature T_(c) ofblood flowing to the dialyzer 302 from the patient access 309. Bloodenters the dialyzers 302 through a valve 332 (optional) and exits thefilter through a valve 334 (optional). The temperature of blood exitingthe filter and entering the venous line T_(v) is indicated bytemperature sensor 314. Blood flows through a venous line 352 and entersthe patient access 309 at a temperature T_(vr) indicated by temperaturesensor 310. Heat from the venous line is transferred at a rate accordingto a lump parameter represented as X_(v). An optional bypass branch 331may be used to circulate blood from the arterial line 350 to the venousline 352 without passing through the dialyzer 302. This may beaccomplished by opening valve 330 and closing valves 332 and 334.

Any of the foregoing components, including temperature sensors andvalves may be omitted depending on the embodiment. Also, treatmentdevices other than dialyzers may be employed, for example it may bereplaced with a hemofilter and replacement fluid line.

FIGS. 14A-14C show sets of control conditions for measuring coretemperature using the embodiments of FIG. 13 according to respectiveembodiments. Each of these figures illustrates a configuration of FIG.13 for implementing any of the embodiments where the patient temperatureTp is estimated using the disclosed embodiments where multiple bloodflow rates are established and for each, at least one temperaturemeasurement Tfi is made to calculate Tp.

Referring now to FIG. 14A, as described above, the dialysate flow may behalted after controlling the temperature of the dialysate in thedialyzer to a normal body temperature. Then blood may be passed throughthe dialyzer 302 without its temperature being continuously changed bythe inflow of fresh dialysate at temperature TDi. As indicated above,this allows the blood temperature to be minimally modified by thermalcontact with dialysate which is held stationary and initialized atnormal body temperature. At any point during a treatment, a temperaturemeasurement cycle may be started wherein the dialyzer temperature isbrought to a normal body temperature or other predefined temperature anda cycle completed according to the above description of the measurementphase of the startup mode, i.e., blood is pumped at two flow rates andT_(fi) is measured at each after establishment of steady state.

Referring to FIG. 14B, the controller of a temperature regulator thatcontrols TDi is regulated for closed loop control to cause T_(v) to beequal to T_(p), where the latter is calculated using the methodsdisclosed where blood is pumped at different flow rates and the patienttemperature is estimated. The estimation of T_(p) may be done using anyof the methods described. Once T_(p) is established, it is used toestimate X_(a) using equation 6. X_(v) may be assumed to be the same atX_(a) or approximated responsively to X_(a). For example, if X_(v) is alonger or shorter tube than X_(a) and both are in the same ambientspace, X_(v) can be scaled according to the difference in lengthaccording to known principles of heat transfer calculations. Then duringa temperature measurement cycle, the T_(v) is calculated from T_(fo)based on X_(v) and an adjusted T_(fo) (Tv-calculated) is activelycontrolled to be equal to T_(a) while the blood flow rate is adjusted tothe two flow rates required to obtain a steady state temperature readingfrom T_(fi) from which the patient core temperature T_(p) can becalculated using the disclosed methods.

Referring to FIG. 14D, the blood temperature is figuratively plottedversus position along the length of the blood circuit. The temperaturefalls as it flows through the arterial line up to the temperature sensorthat measures T_(c). Then the blood temperature continues to fall untilit warmed by contact with heated fluid in the dialyzer (filter F). Thetemperature of the blood is increased to a peak temperature whereupon itfalls again until it is returned. A temperature sensor for the venousline measures temperature T_(v), which is the temperature of the bloodbefore it begins flowing through the venous line. This temperature T_(v)is the control target. The control goal in embodiment of FIG. 14B is toregulate T_(v) such that the final return temperature is the same asT_(p), calculated by the system. The assumption that allows this to bedone is that the external temperature and thermal resistance of thearterial line and the venous lines are the same.

For simplicity, T_(v) may be calculated based on the assumption that theblood temperature in the venous and arterial lines is each uniform alongits length. The ratio of the changes in blood temperature in the venous(T_(v)−T_(p)) and arterial (T_(p)−T_(c)) lines is the same as the ratioof the differences between the average blood temperature in the arterial(T_(ba)) and venous (T_(bv)) lines from the ambient temperature:

$\begin{matrix}{\frac{T_{bv} - T_{a}}{T_{ba} - T_{a}} = {\frac{T_{p} - T_{a} + T_{v} - T_{a}}{T_{p} - T_{a} + T_{c} - T_{a}} = \frac{T_{v} - T_{p}}{T_{p} - T_{c}}}} & (9)\end{matrix}$

Then, solving for T_(v)

$\begin{matrix}{T_{v} = \frac{{2T_{a}T_{p}} - {T_{a}T_{c}} - T_{p}^{2}}{T_{a} - T_{c}}} & (10)\end{matrix}$

Note that the configuration of FIG. 14B may be used for activetemperature control. That is, T_(v) can be compensated for heat loss toobtain a high accuracy estimate for T_(vr) indicated at 310, which maythen be controlled by controlling the temperature regulator for thedialysate (i.e., the heater, cooler, or heater/cooler that determinesTD_(i)) in closed loop fashion. Also note that in additionalembodiments, instead of calculating T_(v) according to equation 10,T_(v) may be taken simply as T_(c)−T_(a) for the current operatingconditions. This estimate would apply where the T_(p)−T_(c) is muchgreater than T_(b)−T_(a). That is the change in the blood temperature(average blood temperature in arterial or venous line being indicated byT_(b)) is much less than the difference between blood temperature andambient such that the rate of heat loss in the venous and arterial linesis approximately the same.

Because the calculation of T_(p) may require the change of blood flow tomultiple different flow rates in order to acquire T_(c1) and T_(c2) orT_(c1), T_(c2), and T_(c3) or other variations (more flow rates could bedone for super-sampling in order to reduce error), any error in thecalculated value of T_(p) may result in a net effect on the patient'sbody temperature. For example, the blood may be returned warmer orcooler than it emerged from the patient resulting in a net heat additionor removal from the patient. To avoid this problem, the patient coretemperature may be calculated, including the acquisition of T_(c1) andT_(c2) or T_(c1), T_(c2), and T_(c3) at the respective flow rates,repeatedly so as to cause the patient's body temperature to converge onits natural (either afebrile or febrile) body temperature. This maypermit more accurate diagnosis of abnormal body temperature andassociated conditions.

Referring to FIG. 14C, for a bypass flow is established by closingvalves 332 and 334 and opening valve 330. Blood flows from the arterialline 350 back to the patient through venous line 352 bypassing thedialyzer 302. This prevents the transfer of heat between the dialysateand the blood thereby preventing the dialysate from affecting thetemperature measurement. The effect is similar to the embodiment of FIG.14A except that the blood temperature is not affect by any difference inthe dialysate temperature in the dialyzer 302 and the temperature of theblood passing through it.

Note that although the target temperature of the above system isidentified as core, it is understood that the patient access may belocated in a peripheral part of the that has a natural normaltemperature that is lower than the patient core temperature. Forexample, a fistula in the arm of a patient may deliver blood at a lowerthan the core temperature of a patient. In every instance where the termcore is used, it may be replaced by a suitable term to reflect thealternative and thus the term is not considered limiting of thedisclosed subject matter.

The above methods may be modified such that the controller outputs to auser interface an instruction to cause the patient to remain still andto maintain steady thermal conditions in the room during temperaturemeasurements. The procedure may include an output of an instruction anda delay until an acknowledgement is indicated by an operator to proceedwith temperature measurement. This may help to ensure that steady stateconditions are established prior to the temperature measurement process(e.g., S40-S48). For example, this operation may be inserted between S38and S40 in FIG. 8.

Since there is no flow in the treatment fluid compartment and thetemperature of the treatment fluid compartment is initialized to anormal body temperature level, the flow in the treatment fluid circuitis substantially adiabatic.

In the embodiments disclosed above, temperature readings are obtainedfor multiple flow rates to enable the solution of a thermal model butfitting a function to it. In embodiments, multiple temperature readingsat different positions along the length of a tube can be obtained topermit the core temperature to be extrapolated. For example, referringto FIG. 7, a temperature T_(a) is sampled at a position L₁ distance froma patient access and a temperature T_(b) is sampled at a position L₂distance from the patient access. In a linear model where thetemperature change is small compared to the temperature differencebetween the fluid and the ambient, the core temperature T_(p) can beobtained from T_(p)=T_(a)+(T_(a)−T_(b))*(L₁/L₂).

The below disclosure provides an embodiment that uses an averagetemperature difference of the blood line.

T_(p)=patient temperature (° C.)T_(c)=sensor temperature (° C.)

T_(b)=(Tb+Tc)/2 (° C.)

T_(a)=ambient temperature (° C.)F=Mass Flow (gm/sec.)F₁=first flow rate; F₂=second flow ratec_(p)=specific heat (Joules/(gm ° C.))=3.78 J/gm° C.P=heat transfer rate (W)Θ=thermal resistance (° C./W)This model makes the following simplifying assumptions:

-   -   1. The blood temperature changes linearly in the line from the        patient to the measurement point which is linear. The blood        temperature is represented as the average of the patient        temperature (T_(p)) and the temperature measured at the sensor        (T_(a)).

T _(b)=(T _(p) +T _(c))/2

-   -   2. The heat transfer rate (power units) from the blood line to        the ambient is given by the difference between the average blood        temperature and the ambient temperature divided by the thermal        resistance Θ.

P=(T _(b) −T _(a))/Θ

-   -   3. The thermal conditions are steady. Specifically, the patient        temperature and the blood heat capacity are constant during a        measurement.        T_(p)−T_(a) (the temperature change in the blood between the        patient and the sensor) is related to the heat transfer rate,        mass flow rate, and heat capacity of the blood.

Heat Capacity Equation for Steady State Flow

P=(T _(p) −T _(c))Fc _(p)

Patient Temperature Calculation:

Assume P is constant for 2 mass flows rates F₁, F₂ and calculate anestimate for Tp. This assumption has a minor inaccuracy because Tb isdifferent for F₁ and F₂.

$T_{p} = \frac{\left( {T_{c\; 1}\; F_{1}} \right) - \left( {T_{c\; 2}\; F_{2}} \right)}{F_{1} - F_{2}}$

Choice of F₁ and F₂:

-   -   F₁ may be chosen as the maximum safe blood flow because high        mass flow reduces the temperature change along the blood line.        F₂ may be chosen to maximize the accuracy of the patient        temperature determination. A relatively low F₂ results in higher        accuracy of measured temperature difference from F₁ and higher        accuracy of flow control difference from F₁ which improve the        accuracy of the calculation. A relatively high F₂ reduces the        change in Tb between the measurements which reduces the error        due to the assumption that the heat loss power is the same for        both flow rates. A temperature measurement and flow control        tolerance analysis along with an analysis of the effect of        different ambient temperatures can be used to determine the        optimal ratio of F₁ to F₂. Rather than using a fixed ratio of F₁        to F₂, in embodiments, the ratio may be adjusted to provide a        fixed difference in Tb between F₁ and F₂.

The foregoing embodiments may be modified by compensating for the changein heat loss power due to the change in the difference between T_(b) andT_(a) at F₂. The ambient temperature (T_(a)) can be measured orotherwise estimated. The approach is as described above with referenceto equations 3b and 3c and more generally according to equation 3a,supra. Note that in a variation, instead of deriving T_(p) as indicated,an estimate or initial guess can be used instead because the improvementprocess described below and elsewhere will converge to an optimum ofT_(p).

Estimate T_(a)

Calculate T_(b1) for F₁:

T _(b1)=(T _(p) +T _(c1))/2

Calculate T_(b2) for F₂

T _(b2)=(T _(p) +T _(c2))/2

Calculate the heat loss to ambient power ratio (Pr) for F₁ to F₂:

Pr=(T _(b1) −T _(a))/(T _(b2) −T _(a))

Calculate the ambient corrected patient temperature:

$T_{p}^{*} = \frac{\left( {T_{c\; 1}\; F_{1}} \right) - \left( {{PrT}_{c\; 2}\; F_{2}} \right)}{F_{1} - \left( {PrF}_{2} \right)}$

This process can be iterated till the new value of T_(p) converges on afinal value.

FIGS. 15A through 15C illustrate the some of the embodiments discussedabove for calculating T_(p) in a format that highlights theirsimilarities and differences. Referring to FIG. 15A, an estimate,measurement, or guess for the ambient temperature is made at S62. Thenthe patient core temperature T_(p) is calculated as discussed above atS64. The average blood temperatures corresponding to each of the bloodflow rates are calculated at A66. A ratio of the heat transfer rates forthe two flow rates is calculated at S68 using the ambient temperature(guess, estimate, or measurement) and the average blood temperatures.The heat transfer rate is used to calculate a revised estimate of thepatient core temperature T_(p)* at S70. At S72 a termination conditionis calculated and if T_(p) is deemed to have converged, execution endsbut if not, the revised core temperature T_(p)* is used in S66 and stepsS66 to S70 repeated until the termination condition is satisfied. In theexample, a difference between the current and revised T_(p)* below athreshold is used to determined convergence of T_(p). A result of anexample calculation using this method is shown in FIG. 16A for one setof simulated conditions.

Referring now to FIG. 15B, the iterative process is the same as in FIG.15A except that instead of using an average temperature difference tocalculate the heat transfer rate ratio at S68, a ratio of log meantemperature difference (LMTD) is calculated at S67, instead. The latteris calculated at S65 from ambient temperature, the initial T_(p), andthe measured temperatures corresponding to the two flow rates. A resultof an example calculation using this method is shown in FIG. 16B for thesame set of simulated conditions as for FIG. 16A.

Referring now to FIG. 15C, the iterative process is as in FIG. 15Bexcept that the ambient temperature guess, estimate, or measurement isiteratively updated S82 to S86 before returning to S65 and after S74.The update of ambient temperature relies on an additional data point,namely, a third flow rate F₃ and a corresponding temperature T_(c3)where the third flow rate is different from the other two, F₁ and F₂. AtS82, equation 6 is used with the first or second flow conditions tocalculate lump parameter X. At S84, the lump parameter X is then pluggedinto equation 8 with the third flow rate F₃ and a correspondingtemperature T_(c3) to calculate a revised ambient temperature. Theambient temperature is set to the new value at S86 and the iterativeprocess repeated until the termination condition is satisfied. A resultof an example calculation using this method is shown in FIG. 16C for thesame set of simulated conditions as for FIGS. 16A and 16B. Note thatFIG. 15C process takes many more iterations but converges to a moreaccurate estimate of the patient core temperature T_(p). Note that avariant of the method of FIG. 15C, an average temperature difference maybe calculated instead of LMTD similar to the method of FIG. 15A. Then Xcan be calculated accordingly using a modified equation 6 that replacesLMTD with the average blood temperature T_(b). Then T_(a) can beobtained from equation 6 solved for T_(a), namely:

$\begin{matrix}{T_{a} = {T_{b} - {\left( {T_{p} - T_{c}} \right)\mspace{11mu}\frac{F}{X}}}} & (9)\end{matrix}$

It will be evident that in the methods embodied in FIG. 15C and variantsan effective temperature of the environment is calculated based on theassumption of a uniform temperature of the external environment of theblood circuit that agrees with the measured temperatures. That is, evenwhere a temperature of the environment of the blood circuit varies, themodels assume a constant external environment temperature and solve forit.

Note that FIGS. 15A-15C are not intended to be comprehensive. The methodof FIG. 15C, for instance, may be modified to use the difference betweenan average blood and the external temperature. Note that ambienttemperature and temperature of the external environment are usedsynonymously here. Note also that the true ambient temperature isindependent of the effective external environment temperature calculatedin certain embodiments.

The above methods may solve, in embodiments, for two parameters, namelya uniform heat transfer resistance and blood inlet temperature T_(p)using two relationships defining the relationship between thetemperature change in the flowing blood along the fluid circuit and thedriving temperature difference between an estimated external environmenttemperature and a blood temperature inside the blood circuit. Inembodiments, an additional unknown, the external environment temperatureis solved for by adding a further relationship based on a third flowrate.

Note that temperatures of blood may be taken along any part of the bloodcircuit including the venous line as long as the calculation used forinferring the core temperature can take into account the heat transferproperties along the entire circuit up to the point of measurement.Also, any of the embodiments may be modified for the measurement of coretemperature using any fluid drawn from the body of the subject at acontrollable rate, which fluid is initially at an equilibriumtemperature with the subject's core. Examples of other fluids arecerebrospinal fluid, urine, ultrafiltrate from an implantable artificialkidney, and spent peritoneal dialysate.

Note that in any of the embodiments, a finite-element dynamic model of atube may be fitted to unsteady state temperature measurements, positionalong the tube, and time. Such a model may have multiple finite elementnodes within the wall of the tube which has properties that may providepredefined thermal capacity and conductivity. The finite element modelmay be segmented along the length of the tube. An analytical model mayalso be employed which is unsteady.

According to embodiments, the disclosed subject matter includes a methodof detecting a fever in a patient undergoing extracorporeal bloodprocessing. The method includes controlling, using an automaticcontroller, a rate of flow of blood through a flow channel connecting apatient to a temperature sensor to establish a first flow rate. Themethod further includes, at the first flow rate, permitting the flow ofan unknown quantity of heat to or from the flow channel connecting apatient to a temperature sensor. At the first flow rate, at least onetemperature of the flow channel is measured using the temperature sensorand first temperature data recorded that is responsive to a result ofthe measuring. Next the method includes controlling, using the automaticcontroller, a rate of flow of blood through the first flow channel toestablish a second flow rate, different from the first and repeating thepermitting and measuring at the second flow rate and recording a secondtemperature data responsively to the corresponding measuring. The methodmay include calculating an inferred temperature from the first andsecond temperature data, the inferred temperature representing atemperature remote from the temperature sensor. The method may furtherinclude comparing the inferred temperature to data responsive to atleast one reference temperature and outputting data to a user interfaceindicating data responsive to a result of the comparing.

To form additional embodiments, any method embodiment may be modifiedsuch that the establishing includes holding the respective first andsecond flow rates for a period of time effective to establish anunchanging temperature indicated by the temperature sensor. To formadditional embodiments, any method embodiment may be modified such thatthe flow channel is an arterial line. To form additional embodiments,any method embodiment may be modified such that the controlling toestablish a first flow rate and the controlling to establish a secondflow rate include flowing at a respective rate for an interval effectiveto establish a steady state condition in terms of heat flow into or outof the fluid channel. To form additional embodiments, any methodembodiment may be modified such that the flow channel is an arterialline. To form additional embodiments, any method embodiment may bemodified such that the permitting includes permitting the flow of heatfrom the flow channel to the ambient environment through a bloodcarrying tube.

According to embodiments, the disclosed subject matter includes a methodof detecting a fever in a patient undergoing extracorporeal bloodprocessing. The method includes controlling, using an automaticcontroller, a rate of flow of blood through a flow channel connecting apatient to a temperature sensor to establish a first flow rate. Themethod includes, at the first flow rate, permitting the flow of anunknown quantity of heat to or from the flow channel connecting apatient to a temperature sensor. The method further includes, at thefirst flow rate, minimizing a flow of heat from or to the flow channelat the temperature sensor and while measuring at least one temperatureof the flow channel using the temperature sensor, the minimizingincluding actively regulating a heat flux to minimize a heat flux fromthe flow channel through the temperature sensor. The method furtherincludes recording a first temperature data responsively to themeasuring and then controlling, using the automatic controller, a rateof flow of blood through the first flow channel to establish a secondflow rate, different from the first. The method includes repeating thepermitting, minimizing, and measuring at the second flow rate andrecording a second temperature data responsively to the correspondingmeasuring and calculating an inferred temperature from the first andsecond temperature data, the inferred temperature representing atemperature remote from the temperature sensor. The method includescomparing the inferred temperature to data responsive to at least onereference temperature and outputting data to a user interface indicatingdata responsive to a result of the comparing.

To form additional embodiments, any method embodiment may be modifiedsuch that the establishing includes holding the respective first andsecond flow rates for a period of time effective to establish anunchanging temperature indicated by the temperature sensor. To formadditional embodiments, any method embodiment may be modified such thatthe flow channel is an arterial line. To form additional embodiments,any method embodiment may be modified such that the controlling toestablish a first flow rate and the controlling to establish a secondflow rate include flowing at a respective rate for an interval effectiveto establish a steady state condition in terms of heat flow into or outof the fluid channel. To form additional embodiments, any methodembodiment may be modified such that the flow channel is an arterialline. To form additional embodiments, any method embodiment may bemodified such that the permitting includes permitting the flow of heatfrom the flow channel to the ambient environment through a bloodcarrying tube. To form additional embodiments, any method embodiment maybe modified such that the data responsive to a condition includes dataindicating that the patient has a fever.

According to embodiments, the disclosed subject matter includes a bloodtreatment system. A blood treatment machine has a programmablecontroller and at least a blood pump whose pumping rate is controlled bythe controller. The blood treatment machine is arranged to receive adisposable blood circuit, the blood treatment machine having atemperature sensor positioned on the blood treatment machine to measurea temperature of blood flowing through an attached blood circuit. Thecontroller is programmed to establish a flow of blood at a first rateaccording to a first predefined condition, whereupon the controllerrecords first temperature data representing a temperature indicated bythe temperature sensor. The controller is programmed subsequently toestablish a flow of blood at a second rate according to a secondpredefined condition, whereupon the controller records secondtemperature data representing a temperature indicated by the temperaturesensor. The controller is programmed to calculate patient temperaturedata indicating a temperature of the fluid circuit responsively to boththe first and second temperature data. And to output a patienttemperature signal to a user interface responsively to the patienttemperature data.

To form additional embodiments, any system embodiment may be modifiedsuch that the patient temperature signal includes an indication that thepatient has a fever. To form additional embodiments, any systemembodiment may be modified to include the comparison by the controllerof the patient temperature data to a predefined range. To formadditional embodiments, any system embodiment may be modified such thatthe first predefined condition and the second predefined condition aretime intervals. To form additional embodiments, any system embodimentmay be modified such that the first predefined condition and the secondpredefined condition are identical time intervals. To form additionalembodiments, any system embodiment may be modified such that the firstpredefined condition and the second predefined condition include adetected establishment of unchanging temperature indicated by thetemperature sensor and determined by the controller. To form additionalembodiments, any system embodiment may be modified such that thetemperature sensor is a contact-type temperature sensor that has asurface temperature element that engages an outside of an attached bloodcircuit.

According to first embodiments, the disclosed subject matter includes amethod of determining a core in a patient undergoing extracorporealblood processing. The method includes controlling, using an automaticcontroller, a rate of flow of blood through a flow channel connecting apatient to a temperature sensor to establish a first flow rate. Themethod includes, at the first flow rate, permitting the flow of anunknown quantity of heat to or from the flow channel connecting apatient to a temperature sensor. The method includes, at the first flowrate, measuring at least one temperature of the flow channel using thetemperature sensor. The method includes, recording a first temperaturedata responsively to said measuring. The method includes controlling,using the automatic controller, a rate of flow of blood through thefirst flow channel to establish a second flow rate, different from thefirst. The method includes repeating the permitting and measuring at thesecond flow rate and recording a second temperature data responsively tothe corresponding measuring. The method includes calculating anextrapolated temperature from the first and second temperature data, theextrapolated temperature representing a temperature remote from thetemperature sensor. The method includes comparing the extrapolatedtemperature to data responsive to at least one reference temperature andoutputting data to a user interface indicating data responsive to aresult of said comparing.

Variations of the first embodiments may be provided to form additionalfirst embodiments in which the establishing includes holding therespective first and second flow rates for a period of time effective toestablish an unchanging temperature indicated by said temperaturesensor. Variations of the first embodiments may be provided to formadditional first embodiments in which the flow channel is an arterialline. Variations of the first embodiments may be provided to formadditional first embodiments in which said controlling to establish afirst flow rate and said controlling to establish a second flow rateinclude flowing at a respective rate for an interval effective toestablish a steady state condition in terms of heat flow into or out ofthe fluid channel. Variations of the first embodiments may be providedto form additional first embodiments in which the flow channel is anarterial line. Variations of the first embodiments may be provided toform additional first embodiments in which the permitting includespermitting the flow of heat from the flow channel to the ambientenvironment through a blood carrying tube.

Variations of the first embodiments may be provided to form additionalfirst embodiments in which the data responsive to a condition includesdata indicating that the patient has a fever.

Variations of the first embodiments may be provided to form additionalfirst embodiments in which the method further includes regulating apatient core temperature by adding or removing heat from the patientand/or patient's blood responsively to a result of the calculating.Variations of the first embodiments may be provided to form additionalfirst embodiments in which the controller is further programmed toregulate the patient core temperature responsively to the calculatedpatient temperature. Variations of the first embodiments may be providedto form additional first embodiments in which the method furtherincludes regulating a patient core temperature by adding or removingheat from the patient and/or patient's blood responsively to a result ofthe calculating, wherein the adding or removing is indicated by apredefined therapeutic treatment modality. Variations of the firstembodiments may be provided to form additional first embodiments inwhich the method further includes regulating a patient core temperatureby adding or removing heat from the patient and/or patient's bloodresponsively to a result of the calculating, wherein the adding orremoving is indicated by a predefined cardiac therapeutic treatmentmodality. Variations of the first embodiments may be provided to formadditional first embodiments in which the method further includesregulating a patient core temperature by adding or removing heat fromthe patient and/or patient's blood responsively to a result of thecalculating, wherein the adding or removing is indicated by a predefinedbrain therapeutic treatment modality.

Variations of the first embodiments may be provided to form additionalfirst embodiments in which the data is responsive to a conditionincludes data indicating that the patient has a fever.

According to second embodiments, the disclosed subject matter includes amethod of detecting a fever in a patient undergoing extracorporeal bloodprocessing. The method includes controlling, using an automaticcontroller, a rate of flow of blood through a flow channel connecting apatient to a temperature sensor to establish a first flow rate. Themethod includes, at the first flow rate, permitting the flow of anunknown quantity of heat to or from the flow channel connecting apatient to a temperature sensor. The method includes, at the first flowrate, minimizing a flow of heat from or to the flow channel at thetemperature sensor and while measuring at least one temperature of theflow channel using the temperature sensor, the minimizing includingactively regulating a heat flux to minimize a heat flux from the flowchannel through the temperature sensor. The method includes recording afirst temperature data responsively to said measuring. The methodincludes controlling, using the automatic controller, a rate of flow ofblood through the first flow channel to establish a second flow rate,different from the first. The method includes repeating the permitting,minimizing, and measuring at the second flow rate and recording a secondtemperature data responsively to the corresponding measuring. The methodincludes calculating an extrapolated temperature from the first andsecond temperature data, the extrapolated temperature representing atemperature remote from the temperature sensor. The method includescomparing the extrapolated temperature to data responsive to at leastone reference temperature and outputting data to a user interfaceindicating data responsive to a result of said comparing.

Variations of the second embodiments may be provided to form additionalsecond embodiments in which the establishing includes holding therespective first and second flow rates for a period of time effective toestablish an unchanging temperature indicated by said temperaturesensor. Variations of the second embodiments may be provided to formadditional second embodiments in which the flow channel is an arterialline. Variations of the second embodiments may be provided to formadditional second embodiments in which said controlling to establish afirst flow rate and said controlling to establish a second flow rateinclude flowing at a respective rate for an interval effective toestablish a steady state condition in terms of heat flow into or out ofthe fluid channel. Variations of the second embodiments may be providedto form additional second embodiments in which the flow channel is anarterial line. Variations of the second embodiments may be provided toform additional second embodiments in which the permitting includespermitting the flow of heat from the flow channel to the ambientenvironment through a blood carrying tube. Variations of the secondembodiments may be provided to form additional second embodiments inwhich the data responsive to a condition includes data indicating thatthe patient has a fever.

Variations of the second embodiments may be provided to form additionalsecond embodiments in which the method further includes regulating apatient core temperature by adding or removing heat from the patientand/or patient's blood responsively to a result of the calculating.Variations of the second embodiments may be provided to form additionalsecond embodiments in which the method further includes regulating apatient core temperature by adding or removing heat from the patientand/or patient's blood responsively to a result of the calculating.Variations of the second embodiments may be provided to form additionalsecond embodiments in which the method further includes regulating apatient core temperature by adding or removing heat from the patientand/or patient's blood responsively to a result of the calculating,wherein the adding or removing is indicated by a predefined therapeutictreatment modality. Variations of the second embodiments may be providedto form additional second embodiments in which the method furtherincludes regulating a patient core temperature by adding or removingheat from the patient and/or patient's blood responsively to a result ofthe calculating, wherein the adding or removing is indicated by apredefined cardiac therapeutic treatment modality. Variations of thesecond embodiments may be provided to form additional second embodimentsin which the method further includes regulating a patient coretemperature by adding or removing heat from the patient and/or patient'sblood responsively to a result of the calculating, wherein the adding orremoving is indicated by a predefined brain therapeutic treatmentmodality.

Variations of the second embodiments may be provided to form additionalsecond embodiments in which the data is responsive to a conditionincludes data indicating that the patient has a fever.

According to third embodiments, the disclosed subject matter includes ablood treatment system that includes a blood treatment machine. Theblood treatment machine has a programmable controller and at least ablood pump whose pumping rate is controlled by the controller. The bloodtreatment machine is arranged to receive a disposable blood circuit. Theblood treatment machine has a temperature sensor positioned on the bloodtreatment machine to measure a temperature of blood flowing through anattached blood circuit. The controller is programmed to establish a flowof blood at a first rate according to a first predefined condition,whereupon the controller records first temperature data representing atemperature indicated by said temperature sensor. The controller isprogrammed subsequently to establish a flow of blood at a second rateaccording to a second predefined condition, whereupon the controllerrecords second temperature data representing a temperature indicated bysaid temperature sensor. The controller is further programmed tocalculate patient temperature data indicating a core patient temperatureresponsively to both said first and second temperature data. Thecontroller is further programmed to output a patient temperature signalto a user interface responsively to said patient temperature data.

Variations of the third embodiments may be provided to form additionalthird embodiments in which the patient temperature signal includes anindication that the patient has a fever. Variations of the thirdembodiments may be provided to form additional third embodiments inwhich the controller compares the patient temperature data to apredefined range and said patient temperature signal is responsive to aresult of such a comparison. Variations of the third embodiments may beprovided to form additional third embodiments in which the firstpredefined condition and the second predefined condition are timeintervals. Variations of the third embodiments may be provided to formadditional third embodiments in which the first predefined condition andthe second predefined condition are identical time intervals. Variationsof the third embodiments may be provided to form additional thirdembodiments in which the first predefined condition and the secondpredefined condition include a detected establishment of unchangingtemperature indicated by said temperature sensor and determined by saidcontroller. Variations of the third embodiments may be provided to formadditional third embodiments in which the temperature sensor is acontact-type temperature sensor that has a surface temperature elementthat engages an outside of an attached blood circuit.

According to fourth embodiments, the disclosed subject matter includes amethod of regulating a patient body temperature. The method includes, ata first time: controlling, using an automatic controller, a rate of flowof blood through a flow channel connecting a patient to a temperaturesensor to establish a first flow rate; at the first flow rate,permitting the flow of an unknown quantity of heat to or from the flowchannel connecting a patient to a temperature sensor; at the first flowrate, measuring at least one temperature of the flow channel using thetemperature sensor; recording a first temperature data responsively tosaid measuring; controlling, using the automatic controller, a rate offlow of blood through the first flow channel to establish a second flowrate, different from the first; repeating the permitting and measuringat the second flow rate and recording a second temperature dataresponsively to the corresponding measuring; calculating an extrapolatedtemperature from the first and second temperature data, the extrapolatedtemperature representing a temperature remote from the temperaturesensor; and comparing the extrapolated temperature to data responsive toat least one reference temperature and outputting data to a userinterface indicating data responsive to a result of said comparing. Themethod includes, at a second time, regulating a patient core temperatureby adding or removing heat from the patient and/or patient's bloodresponsively to a result of the calculating.

Variations of the fourth embodiments may be provided to form additionalfourth embodiments in which the establishing includes holding therespective first and second flow rates for a period of time effective toestablish an unchanging temperature indicated by said temperaturesensor. Variations of the fourth embodiments may be provided to formadditional fourth embodiments in which the flow channel is an arterialline. Variations of the fourth embodiments may be provided to formadditional fourth embodiments in which said controlling to establish afirst flow rate and said controlling to establish a second flow rateinclude flowing at a respective rate for an interval effective toestablish a steady state condition in terms of heat flow into or out ofthe fluid channel. Variations of the fourth embodiments may be providedto form additional fourth embodiments in which the flow channel is anarterial line. Variations of the fourth embodiments may be provided toform additional fourth embodiments in which the permitting includespermitting the flow of heat from the flow channel to the ambientenvironment through a blood carrying tube.

According to fifth embodiments, the disclosed subject matter includes amethod of detecting a fever in a patient undergoing extracorporeal bloodprocessing. The method includes, at a first time: controlling, using anautomatic controller, a rate of flow of blood through a flow channelconnecting a patient to a temperature sensor to establish a first flowrate; at the first flow rate, permitting the flow of an unknown quantityof heat to or from the flow channel connecting a patient to atemperature sensor; at the first flow rate, minimizing a flow of heatfrom or to the flow channel at the temperature sensor and whilemeasuring at least one temperature of the flow channel using thetemperature sensor, the minimizing including actively regulating a heatflux to minimize a heat flux from the flow channel through thetemperature sensor; recording a first temperature data responsively tosaid measuring; controlling, using the automatic controller, a rate offlow of blood through the first flow channel to establish a second flowrate, different from the first; repeating the permitting, minimizing,and measuring at the second flow rate and recording a second temperaturedata responsively to the corresponding measuring; calculating anextrapolated temperature from the first and second temperature data, theextrapolated temperature representing a temperature remote from thetemperature sensor; and comparing the extrapolated temperature to dataresponsive to at least one reference temperature and outputting data toa user interface indicating data responsive to a result of saidcomparing. The method includes, at a second time: regulating a patientcore temperature by adding or removing heat from the patient and/orpatient's blood responsively to a result of the calculating.

Variations of the fifth embodiments may be provided to form additionalfifth embodiments in which the establishing includes holding therespective first and second flow rates for a period of time effective toestablish an unchanging temperature indicated by said temperaturesensor. Variations of the fifth embodiments may be provided to formadditional fifth embodiments in which the flow channel is an arterialline. Variations of the fifth embodiments may be provided to formadditional fifth embodiments in which said controlling to establish afirst flow rate and said controlling to establish a second flow rateinclude flowing at a respective rate for an interval effective toestablish a steady state condition in terms of heat flow into or out ofthe fluid channel. Variations of the fifth embodiments may be providedto form additional fifth embodiments in which the flow channel is anarterial line. Variations of the fifth embodiments may be provided toform additional fifth embodiments in which the permitting includespermitting the flow of heat from the flow channel to the ambientenvironment through a blood carrying tube.

According to sixth embodiments, the disclosed subject matter includes amethod of determining a core in a patient undergoing extracorporealblood processing. The method includes controlling, using an automaticcontroller, a rate of flow of blood through a flow channel connecting apatient to a temperature sensor to establish a first flow rate. Themethod includes at the first flow rate, permitting the flow of anunknown quantity of heat to or from the flow channel connecting apatient to a temperature sensor. The method includes, at the first flowrate, measuring at least one temperature of the flow channel using thetemperature sensor. The method includes recording a first temperaturedata responsively to said measuring. The method includes controlling,using the automatic controller, a rate of flow of blood through thefirst flow channel to establish a second flow rate, different from thefirst. The method includes repeating the permitting and measuring at thesecond flow rate and recording a second temperature data responsively tothe corresponding measuring. The method includes repeating thepermitting and measuring at the third or further flow rates andrecording a corresponding temperature data responsively to each of thecorresponding measuring operations. The method includes calculating atemperature from the first, second, and third or further temperaturedata, the extrapolated temperature representing a temperature remotefrom the temperature sensor, the calculating including computationallyfitting a predefine temperature decay function. The method includescomparing the calculated temperature to data responsive to at least onereference temperature and outputting data to a user interface indicatingdata responsive to a result of said comparing.

Variations of the sixth embodiments may be provided to form additionalsixth embodiments in which the establishing includes holding therespective first and second flow rates for a period of time effective toestablish an unchanging temperature indicated by said temperaturesensor. Variations of the sixth embodiments may be provided to formadditional sixth embodiments in which the flow channel is an arterialline. Variations of the sixth embodiments may be provided to formadditional sixth embodiments in which said controlling to establish afirst flow rate and said controlling to establish a second flow rateinclude flowing at a respective rate for an interval effective toestablish a steady state condition in terms of heat flow into or out ofthe fluid channel. Variations of the sixth embodiments may be providedto form additional sixth embodiments in which the flow channel is anarterial line. Variations of the sixth embodiments may be provided toform additional sixth embodiments in which the permitting includespermitting the flow of heat from the flow channel to the ambientenvironment through a blood carrying tube.

According to seventh embodiments, the disclosed subject matter includesa blood treatment system that includes a blood treatment machine. Theblood treatment machine has a programmable controller and at least ablood pump whose pumping rate is controlled by the controller. The bloodtreatment machine is arranged to receive a disposable blood circuit. Theblood treatment machine has a plurality of temperature sensorspositioned on the blood treatment machine and/or an attached bloodcircuit to measure respective temperatures of blood flowing through anattached blood circuit. The controller is programmed to establish a flowof blood at a first rate according to a first predefined condition,whereupon the controller records first temperature data representing atemperature indicated by said plurality of temperature sensors. Thecontroller is programmed subsequently to establish a flow of blood at asecond rate according to a second predefined condition, whereupon thecontroller records second temperature data representing a temperatureindicated by said plurality of temperature sensors. The controller isfurther programmed to calculate a core patient temperature responsivelyto both said first and second temperature data, the core temperaturecalculation including fitting a decay function the temperaturesindicated by said plurality of temperature sensors. The controller isfurther programmed to output a patient temperature signal to a userinterface responsively to said patient temperature data.

Variations of the seventh embodiments may be provided to form additionalseventh embodiments in which the patient temperature signal includes anindication that the patient has a fever. Variations of the seventhembodiments may be provided to form additional seventh embodiments inwhich the controller compares the patient temperature data to apredefined range and said patient temperature signal is responsive to aresult of such a comparison. Variations of the seventh embodiments maybe provided to form additional seventh embodiments in which the firstpredefined condition and the second predefined condition are timeintervals. Variations of the seventh embodiments may be provided to formadditional seventh embodiments in which the first predefined conditionand the second predefined condition are identical time intervals.Variations of the seventh embodiments may be provided to form additionalseventh embodiments in which the first predefined condition and thesecond predefined condition include a detected establishment ofunchanging temperature indicated by said temperature sensor anddetermined by said controller. Variations of the seventh embodiments maybe provided to form additional seventh embodiments in which thetemperature sensor is a contact-type temperature sensor that has asurface temperature element that engages an outside of an attached bloodcircuit.

According to eight embodiments, the disclosed subject matter includes ablood with a blood pump and a temperature sensor. The blood pump andtemperature sensor are configured to receive a predefined fluid circuithaving a blood circuit. The blood circuit may or may not form part ofthe disclosed embodiment but the form of the embodiment may be limitedby the predefined blood circuit. A controller connects to the blood pumpto control a speed thereof and to the temperature sensor to receive atemperature signal output therefrom. The temperature sensor isconfigured to detect a temperature of blood carried by the bloodcircuit. the controller is programmed to operate the pump at at leasttwo flow rates, record first and second temperature data responsive tothe temperature signal at each flow rate, respectively and to calculatea core temperature, responsive to both the first and second temperaturedata, where the core temperature is an estimation of the temperature ata point in said blood circuit remote from the temperature sensor andcompensates for a temperature change in flowing blood between said pointand said temperature sensor.

Variations of the eighth embodiments may be provided to form additionaleighth embodiments in which the controller is connected to a userinterface with a display and is further programmed to show said coretemperature on said display. Variations of the eighth embodiments may beprovided to form additional eighth embodiments that include a treatmentfluid pump connected for control by said controller, the treatment fluidpump engaging a treatment fluid circuit of said predefined fluidcircuit. The controller may be further programmed to operate said bloodpump at said at least two flow rates during a temperature measurementphase of a startup mode of said blood treatment system. Variations ofthe eighth embodiments may be provided to form additional eighthembodiments in which in the temperature measurement phase of the startupmode the controller controls the treatment fluid pump to prevent flow inthe treatment fluid circuit. Variations of the eighth embodiments may beprovided to form additional eighth embodiments in which the predefinedfluid circuit has treatment device that forms a heat transfer interfacebetween the treatment fluid circuit and the blood circuit such that heatis transferred between the blood in the blood circuit and treatmentfluid in the treatment fluid circuit. Variations of the eighthembodiments may be provided to form additional eighth embodiments thatinclude a temperature regulator that engages the treatment fluidcircuit. The controller controls the temperature regulator to bring atreatment fluid to a predefined temperature in said treatment fluiddevice prior to said temperature measurement phase. Variations of theeighth embodiments may be provided to form additional eighth embodimentsin which the controller is configured to control the temperatureregulator and flushes the treatment device prior to said treatmentmeasurement phase to fill a blood compartment of said treatment devicewith treatment fluid at said predefined temperature. Variations of theeighth embodiments may be provided to form additional eighth embodimentsin which the predefined temperature is a normal body temperature.Variations of the eighth embodiments may be provided to form additionaleighth embodiments in which the controller is programmed to calculate acore temperature based on a constant heat transfer rate for all of saidat least two flow rates. Variations of the eighth embodiments may beprovided to form additional eighth embodiments in which the controlleris programmed to calculate a core temperature responsively to an initialestimate of the core temperature that is based on the constant heattransfer rate and responsively to an improved core temperature estimateresponsively to the initial estimate of the core temperature, anestimated or measured of an ambient temperature, and the at least twoflow rates. Variations of the eighth embodiments may be provided to formadditional eighth embodiments in which the improved core temperatureestimate is responsive to a difference between the estimated or measuredambient temperature and an average of the initial estimate of the coretemperature and the temperature indicated by said temperature signal.

According to ninth embodiments, the disclosed subject matter includes ablood treatment method. The method includes providing a blood pump and atemperature sensor, the blood pump and temperature sensor is configuredto receive a predefined fluid circuit having a blood circuit. The methodincludes providing a controller connected to the blood pump to control aspeed thereof and to the temperature sensor to receive a temperaturesignal output therefrom. The temperature sensor is configured to detecta temperature of blood carried by the blood circuit. The method includesusing the controller, operating the pump at at least two flow rates. Themethod includes, for each of the at least two flow rates, using thecontroller, recording first and second temperature data responsive tothe temperature signal at each of said at least two flow rates. Themethod includes using the controller, calculating a core temperatureresponsively to both the first and second temperature data such that thecore temperature is an estimation of the temperature at a point in saidblood circuit remote from the temperature sensor and the calculatingcompensates for a temperature change in flowing blood between said pointand said temperature sensor.

Variations of the ninth embodiments may be provided to form additionalninth embodiments that include using the controller display said coretemperature a display of a user interface. Variations of the ninthembodiments may be provided to form additional ninth embodiments thatinclude using the controller, controlling a treatment fluid pumpconnected, the treatment fluid pump engaging a treatment fluid circuitof said predefined fluid circuit and controlling a treatment fluid pumpincludes operating said blood pump at said at least two flow ratesduring a temperature measurement phase of a startup mode of said bloodtreatment system, the startup mode includes priming said blood circuit.Variations of the ninth embodiments may be provided to form additionalninth embodiments in which, during temperature measurement phase of thestartup mode, using the controller, controlling the treatment fluid pumpto prevent flow in the treatment fluid circuit. Variations of the ninthembodiments may be provided to form additional ninth embodiments inwhich the predefined fluid circuit has treatment device that forms aheat transfer interface between the treatment fluid circuit and theblood circuit such that heat is transferred between the blood in theblood circuit and treatment fluid in the treatment fluid circuit.Variations of the ninth embodiments may be provided to form additionalninth embodiments in which a temperature regulator engages the treatmentfluid circuit, further comprising, using the controller, controlling thetemperature regulator and said treatment fluid pump, bringing atreatment fluid to a predefined temperature in said treatment fluiddevice prior to said temperature measurement phase. Variations of theninth embodiments may be provided to form additional ninth embodimentsthat include, using the controller, controlling the temperatureregulator and flushes the treatment device prior to said treatmentmeasurement phase to fill a blood compartment of said treatment devicewith treatment fluid at said predefined temperature. Variations of theninth embodiments may be provided to form additional ninth embodimentsin which the predefined temperature is a normal body temperature.Variations of the ninth embodiments may be provided to form additionalninth embodiments in which the calculating a core temperature includescalculating based on a constant heat transfer rate for all of said atleast two flow rates. Variations of the ninth embodiments may beprovided to form additional ninth embodiments in which the calculatingincludes calculating a core temperature responsively to an initialestimate of the core temperature that is based on the constant heattransfer rate and responsively to an improved core temperature estimateresponsively to the initial estimate of the core temperature, anestimated or measured of an ambient temperature, and the at least twoflow rates. Variations of the ninth embodiments may be provided to formadditional ninth embodiments in which the improved core temperatureestimate is responsive to a difference between the estimated or measuredambient temperature and an average of the initial estimate of the coretemperature and the temperature indicated by said temperature signal.

According to tenth embodiments, the disclosed subject matter includes amethod of detecting a blood temperature in a blood treatment circuit.The method includes estimating a steady state heat transfercharacteristic of a fluid circuit, the estimate is calculatedinferentially from a temperature measurement of a fluid flow in a bloodcircuit. The method includes storing said heat transfer characteristicand calculating from it, a temperature at a point in said blood circuitremote from a point where the temperature measurement was taken. Themethod includes measuring a change in the temperature and calculatingwhether that change indicates a possible change in the heat transfercharacteristic. The method includes repeating said estimatingresponsively to an outcome of said calculating.

According to eleventh embodiments, the disclosed subject matterincludes, a blood treatment system. A blood pump and a temperaturesensor, the blood pump and temperature sensor is configured to receive apredefined fluid circuit has a blood circuit with a blood inlet. Acontroller is connected to the blood pump to control a speed thereof andto the temperature sensor to receive a temperature signal outputtherefrom. The temperature sensor is configured to detect a temperatureof blood carried by the blood circuit. The controller is programmed tooperate the pump at at least two flow rates, record first and secondtemperature data responsive to the temperature signal at each flow rate,respectively and to calculate an inlet temperature at the blood inlet,responsive to both the first and second temperature data, where theinlet temperature is an estimation of the temperature at a point in theblood circuit remote from the temperature sensor and compensates for atemperature change in flowing blood between the point and thetemperature sensor. Further eleventh embodiments include ones in whichthe controller is connected to a user interface with a display and isfurther programmed to show the inlet temperature on the display.

Further eleventh embodiments include ones that include a treatment fluidpump connected for control by the controller, the treatment fluid pumpengaging a treatment fluid circuit of the predefined fluid circuit. Thecontroller is further programmed to operate the blood pump at the atleast two flow rates during a temperature measurement phase of a startupmode of the blood treatment system.

Further eleventh embodiments include ones in which in the temperaturemeasurement phase of the startup mode the controller controls thetreatment fluid pump to prevent flow in the treatment fluid circuit.

Further eleventh embodiments include ones in which the predefined fluidcircuit has a treatment device that forms a heat transfer interfacebetween the treatment fluid circuit and the blood circuit such that heatis transferred between the blood in the blood circuit and treatmentfluid in the treatment fluid circuit.

Further eleventh embodiments include ones that include a temperatureregulator that engages the treatment fluid circuit, wherein thecontroller controls the temperature regulator to bring a treatment fluidto a predefined temperature in the treatment fluid device prior to thetemperature measurement phase.

Further eleventh embodiments include ones in which the controller isconfigured to control the temperature regulator and flushes thetreatment device prior to the treatment measurement phase to fill ablood compartment of the treatment device with treatment fluid at thepredefined temperature.

Further eleventh embodiments include ones in which the predefinedtemperature is a normal body temperature.

Further eleventh embodiments include ones in which the controller isprogrammed to calculate the inlet temperature based on a constant heattransfer rate for all of the at least two flow rates.

Further eleventh embodiments include ones in which the controller isprogrammed to calculate the inlet temperature responsively to an initialestimate of the inlet temperature that is based on the constant heattransfer rate and responsively to an improvement in the inlettemperature estimate responsively to the initial estimate of the inlettemperature, an estimated or measured of an ambient temperature, and theat least two flow rates.

Further eleventh embodiments include ones in which the improved inlettemperature estimate is responsive to a difference between the estimatedor measured ambient temperature and an average of the initial estimateof the inlet temperature and the temperature indicated by thetemperature signal.

According to twelfth embodiments, the disclosed subject matter includes,a blood treatment method. The method includes providing a blood pump anda temperature sensor, the blood pump and temperature sensor isconfigured to receive a predefined fluid circuit has a blood circuitwith a blood inlet. The method further includes providing a controllerconnected to the blood pump to control a speed thereof and to thetemperature sensor to receive a temperature signal output therefrom. Thetemperature sensor is configured to detect a temperature of bloodcarried by the blood circuit. The method further includes using thecontroller, operating the pump at at least two flow rates. The methodfurther includes, for each of the at least two flow rates, using thecontroller, recording first and second temperature data responsive tothe temperature signal at each of the at least two flow rates. Themethod further includes using the controller, calculating an inlettemperature responsively to both the first and second temperature datasuch that the inlet temperature is an estimation of the temperature at apoint in the blood circuit remote from the temperature sensor and thecalculating compensates for a temperature change in flowing bloodbetween the point and the temperature sensor. Further twelfthembodiments include ones in which using the controller display the inlettemperature a display of a user interface.

Further twelfth embodiments include ones that include using thecontroller, controlling a treatment fluid pump connected, the treatmentfluid pump engaging a treatment fluid circuit of the predefined fluidcircuit. controlling a treatment fluid pump includes operating the bloodpump at the at least two flow rates during a temperature measurementphase of a startup mode of the blood treatment system, the startup modeincludes priming the blood circuit.

Further twelfth embodiments include ones in which during temperaturemeasurement phase of the startup mode, using the controller, controllingthe treatment fluid pump to prevent flow in the treatment fluid circuit.

Further twelfth embodiments include ones in which the predefined fluidcircuit has treatment device that forms a heat transfer interfacebetween the treatment fluid circuit and the blood circuit such that heatis transferred between the blood in the blood circuit and treatmentfluid in the treatment fluid circuit.

Further twelfth embodiments include ones in which a temperatureregulator engages the treatment fluid circuit, further comprising, usingthe controller, controlling the temperature regulator and the treatmentfluid pump, bringing a treatment fluid to a predefined temperature inthe treatment fluid device prior to the temperature measurement phase.

Further twelfth embodiments include ones that include using thecontroller, controlling the temperature regulator and flushes thetreatment device prior to the treatment measurement phase to fill ablood compartment of the treatment device with treatment fluid at thepredefined temperature.

Further twelfth embodiments include ones in which the predefinedtemperature is a normal body temperature.

Further twelfth embodiments include ones in which the calculating theinlet temperature includes calculating based on a constant heat transferrate for all of the at least two flow rates.

Further twelfth embodiments include ones in which the calculating theinlet temperature is responsive to an initial estimate of the inlettemperature that is based on the constant heat transfer rate andresponsively to an improved inlet temperature estimate responsively tothe initial estimate of the inlet temperature, an estimated or measuredof an ambient temperature, and the at least two flow rates.

Further twelfth embodiments include ones in which the improved inlettemperature estimate is responsive to a difference between the estimatedor measured ambient temperature and an average of the initial estimateof the inlet temperature and the temperature indicated by thetemperature signal.

According to thirteenth embodiments, the disclosed subject matterincludes, a method of detecting a blood temperature in a blood treatmentcircuit. The method includes estimating a steady state heat transfercharacteristic of a fluid circuit, the estimate is calculatedinferentially from a temperature measurement of a fluid flow in a bloodcircuit. The method further includes storing the heat transfercharacteristic and calculating from it, a temperature at a point in theblood circuit remote from a point where the temperature measurement wastaken. The method further includes measuring a change in the temperatureand calculating whether that change indicates a possible change in theheat transfer characteristic. The method further includes repeating theestimating responsively to an outcome of the calculating.

According to fourteenth embodiments, the disclosed subject matterincludes a fluid temperature method. The method includes providing afluid pump and a temperature sensor, the fluid pump and temperaturesensor is configured to receive a predefined fluid circuit. The methodfurther includes providing a controller connected to the fluid pump tocontrol a speed thereof and to the temperature sensor to receive atemperature signal output therefrom. The method further includes thetemperature sensor is configured to detect a temperature of fluidcarried by the fluid circuit. The method further includes using thecontroller, operating the pump at at least two flow rates. The methodfurther includes, for each of the at least two flow rates, using thecontroller, recording first and second temperature data responsive tothe temperature signal at each of the at least two flow rates. Themethod further includes using the controller, calculating an inlettemperature responsively to both the first and second temperature datasuch that the inlet temperature is an estimation of the temperature at apoint in the fluid circuit remote from the temperature sensor and thecalculating compensates for a temperature change in flowing fluidbetween the point and the temperature sensor. Further fourteenthembodiments include ones that include using the controller, displayingthe inlet temperature a display of a user interface.

Further fourteenth embodiments include ones that include using thecontroller, controlling a treatment fluid pump connected, the treatmentfluid pump engaging a treatment fluid circuit of the predefined fluidcircuit. controlling a treatment fluid pump includes operating the fluidpump at the at least two flow rates during a temperature measurementphase of a startup mode of the fluid treatment system, the startup modeincludes priming the fluid circuit.

Further fourteenth embodiments include ones in which, during temperaturemeasurement phase of the startup mode, using the controller, controllingthe treatment fluid pump to prevent flow in the treatment fluid circuit.

Further fourteenth embodiments include ones in which the predefinedfluid circuit has treatment device that forms a heat transfer interfacebetween the treatment fluid circuit and the fluid circuit such that heatis transferred between the fluid in the fluid circuit and treatmentfluid in the treatment fluid circuit.

Further fourteenth embodiments include ones in which a temperatureregulator engages the treatment fluid circuit, further comprising, usingthe controller, controlling the temperature regulator and the treatmentfluid pump, bringing a treatment fluid to a predefined temperature inthe treatment fluid device prior to the temperature measurement phase.

Further fourteenth embodiments include ones that include, using thecontroller, controlling the temperature regulator and flushes thetreatment device prior to the treatment measurement phase to fill afluid compartment of the treatment device with treatment fluid at thepredefined temperature.

Further fourteenth embodiments include ones in which the predefinedtemperature is a normal body temperature.

Further fourteenth embodiments include ones in which the calculating aninlet temperature includes calculating based on a constant heat transferrate for all of the at least two flow rates.

Further fourteenth embodiments include ones in which the calculatingincludes calculating the inlet temperature responsively to an initialestimate of the inlet temperature that is based on the constant heattransfer rate and responsively to an improved inlet temperature estimateresponsively to the initial estimate of the inlet temperature, anestimated or measured of an ambient temperature, and the at least twoflow rates.

Further fourteenth embodiments include ones in which the improved inlettemperature estimate is responsive to a difference between the estimatedor measured ambient temperature and an average of the initial estimateof the inlet temperature and the temperature indicated by thetemperature signal.

Further fourteenth embodiments include ones in which the fluid is blood.

Further fourteenth embodiments include ones in which the fluid is spentperitoneal dialysate.

Further fourteenth embodiments include ones in which the fluid is urine.

Further fourteenth embodiments include ones in which the treatment fluidis dialysate.

Further fourteenth embodiments include ones in which the treatment fluidis a gas.

According to fifteenth embodiments, the disclosed subject matterincludes, a method of estimating a temperature T_(p) of the blood of apatient connected to an extracorporeal blood treatment device, themethod is implemented automatically by a controller operable with theextracorporeal blood treatment device, the controller is connected to apump, a sensor, and a user interface. The method includes using thecontroller, pumping blood in a blood circuit from a patient accessthrough the blood circuit to a temperature sensor positioned along theblood circuit remote from the patient access such that heat istransferred between the blood and the external environment of the bloodcircuit as the blood flows from the access to the temperature sensor.The pumping includes, automatically, using the controller, pumping bloodat a first flow rate F₁ and then subsequently pumping blood at a secondflow rate F₂, recording temperatures T_(c1) and T_(c2), respectively,for each of the flow rates, calculating a temperature T_(p) fromtemperatures T_(c1) and T_(c2) and flows F₁ and F₂, and outputting dataresponsive to the calculated T_(p).

Further fifteenth embodiments include ones in which the calculating isindependent of a measured temperature of the external environment.

Further fifteenth embodiments include ones in which the calculatinginitially uses an estimated or standard temperature of the externalenvironment but calculates an effective temperature of the externalenvironment.

Further fifteenth embodiments include ones in which the calculatingincludes calculating T_(p) by finding a common intercept of two lines,each is proportional to the same constant heat transfer rate andinversely proportional, respectively, to F₁ and F₂.

Further fifteenth embodiments include ones in which T_(p) is calculatingfrom: T_(p)=[(T_(c1)*F₁)−(T_(c2)*F₂)]/(F₁−F₂).

Further fifteenth embodiments include ones in which F₁ is a maximum safeblood flow rate of the extracorporeal blood treatment device.

Further fifteenth embodiments include ones in which F₂ is between 40 and60% of F₁.

Further fifteenth embodiments include ones in which F₂ is between 50% ofF₁.

Further fifteenth embodiments include ones that include revising theestimate of T_(p) before the outputting, the revising includes using aninitial estimate of the temperature of the environment, iterativelysolving for an effective temperature of the environment.

Further fifteenth embodiments include ones that include revising theestimate of T_(p) before the outputting, the revising includes using aninitial estimate of the temperature of the environment to calculateindependent heat transfer rates corresponding to each of the conditionscorresponding to T_(c1) and T_(c2).

Further fifteenth embodiments include ones in which the revising furtherincludes iteratively refining the estimate of Tb using a singletemperature of the environment.

Further fifteenth embodiments include ones in which the revising furtherincludes iteratively refining the estimate of Tb by estimatingT_(a)=temperature of the environment and solving for a power rate equalto a ratio of a characteristic temperature of the blood at each of F₁and F₂, the characteristic temperature depending on a prior estimate ofT_(p), and using the power rate to calculate an updated estimate ofT_(p) and then repeating with the updated estimate until it converges.

Further fifteenth embodiments include ones in which the using the powerrate includes calculating T_(p)*=[(T_(c1)*F₁)−(PrT_(c2)*F₂)]/[F₁−(Pr*F₂)], where Pr is the most recent power rate andT_(p)* is a new estimate for T_(p).

Further fifteenth embodiments include ones in which Pr is calculated ateach iteration according to Pr=(T_(b1)−T_(a))/(T_(b2)−T_(a)), whereT_(b1)=(T_(p)+T_(c1))/2, T_(b2)=(T_(p)+T_(c2))/2, and T_(a) is thetemperature of the environment.

Further fifteenth embodiments include ones in which Pr is calculated ateach iteration according to Pr=LMTD (T_(c1), T_(p)*, T_(a))/LMTD(T_(c2), T_(p)*, T_(a)), where LMTD (Tc, T_(p),T_(a))=(T_(c)−T_(a))−(T_(p)−T_(a))/ln[(Tc−T_(a))/(T_(p)−T_(a))].

According to sixteenth embodiments, the disclosed subject matterincludes, a method of estimating a temperature T_(p) of the blood of apatient connected to an extracorporeal blood treatment device, themethod is implemented automatically by a controller operable with theextracorporeal blood treatment device, the controller is connected to apump, a sensor, and a user interface. The method includes using thecontroller, pumping blood from a patient access through a blood circuitto a temperature sensor positioned along the blood circuit remote fromthe patient access such that heat is transferred between the blood andthe external environment of the blood circuit as the blood flows fromthe access to the temperature sensor. The pumping includes,automatically, using the controller, pumping blood at a first flow rateF₁ and then subsequently pumping blood at a second flow rate F₂,recording temperatures T_(c1) and T_(c2), respectively, for each of theflow rates, calculating a temperature T_(p) from temperatures T_(c1) andT_(c2) and flows F₁ and F₂. wherein the calculating implicitly employsan effective temperature difference between the blood temperature and aneffective temperature of the external environment of the blood circuitfor each of the F₁ and F₂.

Further sixteenth embodiments include ones in which the effectivetemperature of the environment is a temperature that is calculated basedon the assumption of a uniform temperature of the external environmentof the blood circuit that agrees with the measured temperatures.

Further sixteenth embodiments include ones in which the effectivetemperature of the environment is a temperature that is calculated basedon the assumption of a uniform temperature of the external environmentof the blood circuit that agrees with the measured temperatures theeffective temperature of the environment is iteratively calculated.

Further sixteenth embodiments include ones in which the methods arecarried out automatically by a computer connected to a blood processingmachine.

Further sixteenth embodiments include ones in which the methods arecarried out automatically by a computer connected to a hemodialysismachine.

Further sixteenth embodiments include ones in which the methods arecarried out automatically by a computer connected to a dialysis machine.

According to seventeenth embodiments, the disclosed subject matterincludes, a method of calculating a blood return temperature. The methodincludes pumping blood from a patient using an extracorporeal bloodprocessing machine, the pumping includes pumping blood at multiple flowrates. The method further includes measuring blood temperatures in ablood circuit at a first temperature sensor located remote from apatient access, connected by an arterial portion thereof, for each ofthe multiple flow rates. The method further includes calculating a heattransfer characteristic of the blood circuit from the patient access tothe first temperature sensor responsively to the multiple flow rates andthe respective temperatures. The method further includes calculating areturn temperature at a patient access end of a venous portion of theblood circuit that returns blood to the patient.

Further seventeenth embodiments include ones in which the calculating areturn temperature includes measuring a temperature at a secondtemperature located remote from the patient access and connected by thevenous portion of the blood circuit.

Further seventeenth embodiments include ones in which the venous andarterial portions of the blood circuit are parallel channels.

Further seventeenth embodiments include ones in which the venous andarterial portions of the blood circuit are parallel tubes over a majorfraction thereof.

Further seventeenth embodiments include ones in which temperature sensoris an active temperature sensor that measures temperature by activelycanceling heat flux in a wall of a fluid circuit separating atemperature sensor and the fluid whose temperature is to be measured.

Further seventeenth embodiments include ones that include using acontroller of the extracorporeal blood processing machine, calculating aheat transfer parameter of the blood circuit, the heat transferparameter is responsive to a thermal resistance of a wall of the bloodcircuit.

According to eighteenth embodiments, the disclosed subject matterincludes, a method of calculating a blood return temperature. The methodincludes pumping blood from a patient using an extracorporeal bloodprocessing machine, the pumping includes pumping blood at multiple flowrates. The method further includes measuring blood temperatures, andrecording them, in a blood circuit at a first temperature sensor locatedremote from a patient access, connected by an arterial portion thereof,for each of the multiple flow rates. The method further includescalculating a heat transfer characteristic of the blood circuit from thepatient access to the first temperature sensor responsively to themultiple flow rates and the respective temperatures. The method furtherincludes using the heat transfer characteristic, regulating a returntemperature at a patient access end of a venous portion of the bloodcircuit that returns blood to the patient.

Further eighteenth embodiments include ones in which the regulating iseffective to maintain a body temperature of a patient in a predefinedrange.

Further eighteenth embodiments include ones in which the regulatingincludes compensating for heat transfer in the venous portion betweenblood carried thereby and an external environment of the venous portion.

Further eighteenth embodiments include ones that include detecting acondition indicating that the heat transfer characteristic has changedand, responsively thereto, repeating the pumping blood at multiple flowrates and calculating a heat transfer characteristic responsively to aresult of the detecting.

Further eighteenth embodiments include ones in which the detecting acondition includes a predefined change in the temperature indicated bythe first temperature sensor.

Further eighteenth embodiments include ones in which the detectingincludes detecting a mechanical movement of the blood circuit.

Further eighteenth embodiments include ones that include detecting asteady state of the heat transfer characteristic, wherein the recordingis responsive to the detecting a stead state.

According to nineteenth embodiments, the disclosed subject matterincludes, a method of calculating a patient blood temperature. Themethod includes pumping blood from a patient using an extracorporealblood processing machine, the pumping includes pumping blood at multipleflow rates. The method further includes measuring blood temperatures ina blood circuit at a first temperature sensor located remote from apatient access, connected by an arterial portion thereof, for each ofthe multiple flow rates. The method further includes calculating a heattransfer characteristic of the blood circuit from the patient access tothe first temperature sensor responsively to the multiple flow rates andthe respective temperatures. The method further includes using the heattransfer characteristic, calculating a patient body temperature includescompensating for heat transfer between the patient access and thetemperature sensor based on the heat transfer characteristic.

Further nineteenth embodiments include ones in which the heat transfercharacteristic is responsive to a heat transfer coefficient and atemperature of an environment of the arterial portion.

Further nineteenth embodiments include ones that include recording thecalculating body temperature to a treatment log corresponding to thepatient.

Further nineteenth embodiments include ones that include outputting asignal responsively to a comparison between data in the treatment logand a temperature resulting from the calculating.

Further nineteenth embodiments include ones that include recording thecalculating body temperature to a treatment log corresponding to thepatient, the recording includes recording a time series of temperaturesover an interval of a treatment.

Further nineteenth embodiments include ones that include outputting asignal responsively to a comparison between data in the treatment logand a temperature resulting from the calculating.

Further nineteenth embodiments include ones that include repeating thepumping blood at multiple flow rates and calculating a heat transfercharacteristic of the blood circuit in response to the lapse of a timer.

Further nineteenth embodiments include ones that include repeating thepumping blood at multiple flow rates and calculating a heat transfercharacteristic of the blood circuit in response to the lapse of a timerinitialized at the beginning of a blood treatment.

In any of the disclosed embodiments, any recited calculations may beperformed by the controller of a blood processing machine.

According to twentieth embodiments, the disclosed subject matterincludes, a blood treatment system. The system includes a controller, ablood pump and a temperature sensor, the blood pump and temperaturesensor is configured to receive a predefined fluid circuit has a bloodcircuit with a blood inlet. The controller is connected to the bloodpump to control a speed thereof and to the temperature sensor to receivea temperature signal output therefrom. The temperature sensor isconfigured to detect a temperature of blood carried by the bloodcircuit. The controller is programmed operate the pump at at least twoflow rates during a temperature measurement operation. For each of theat least two flow rates, the controller records first and secondtemperature data responsive to the temperature signal at each of the atleast two flow rates. The controller calculates an inlet temperatureresponsively to both the first and second temperature data such that theinlet temperature is an estimation of the temperature at a point in theblood circuit remote from the temperature sensor where the calculationcompensates for a temperature change in flowing blood between the pointand the temperature sensor.

Further twentieth embodiments include ones in which the controllerdisplays the inlet temperature a display of a user interface.

Further twentieth embodiments include ones in which the controllercontrols a treatment fluid pump connected, the treatment fluid pumpengaging a treatment fluid circuit of the predefined fluid circuit andcontrols a treatment fluid pump and operates the blood pump at the atleast two flow rates during a temperature measurement phase of a startupmode of the blood treatment system, the startup mode includes primingthe blood circuit.

Further twentieth embodiments include ones in which, during thetemperature measurement phase of the startup mode, the controllercontrols the treatment fluid pump to prevent flow in the treatment fluidcircuit.

Further twentieth embodiments include ones in which the predefined fluidcircuit has treatment device that forms a heat transfer interfacebetween the treatment fluid circuit and the blood circuit such that heatis transferred between the blood in the blood circuit and treatmentfluid in the treatment fluid circuit.

Further twentieth embodiments include ones in which a temperatureregulator engages the treatment fluid circuit and the controllercontrols the temperature regulator and the treatment fluid pump,bringing a treatment fluid to a predefined temperature in the treatmentfluid device prior to the temperature measurement phase.

Further twentieth embodiments include ones in which the controllercontrols the temperature regulator and flushes the treatment deviceprior to the treatment measurement phase to fill a blood compartment ofthe treatment device with treatment fluid at the predefined temperature.

Further twentieth embodiments include ones in which the predefinedtemperature is a normal body temperature.

Further twentieth embodiments include ones in which the inlettemperature is calculated based on a constant heat transfer rate for allof the at least two flow rates.

Further twentieth embodiments include ones in which the inlettemperature is calculated responsive to an initial estimate of the inlettemperature that is based on the constant heat transfer rate andresponsively to an improved inlet temperature estimate responsively tothe initial estimate of the inlet temperature, an estimated or measuredof an ambient temperature, and the at least two flow rates.

Further twentieth embodiments include ones in which the improved inlettemperature estimate is responsive to a difference between the estimatedor measured ambient temperature and an average of the initial estimateof the inlet temperature and the temperature indicated by thetemperature signal.

According to twenty-first embodiments, the disclosed subject matterincludes, a system for detecting a blood temperature in a bloodtreatment circuit. A blood treatment machine has a controller, thecontrolling is programmed to estimate a steady state heat transfercharacteristic of a fluid circuit attached to the blood treatmentmachine to generate an estimate by calculating inferentially from atemperature measurements of a blood flow in a blood circuit andcorresponding blood flow rates. The controller stores the heat transfercharacteristic and calculating from it, a temperature at a point in theblood circuit remote from a point where the temperature measurement wastaken. The controller further measures a change in the temperature andcalculating whether that change indicates a possible change in the heattransfer characteristic and repeating the estimating responsively to anoutcome of the calculating.

According to twenty-second embodiments, the disclosed subject matterincludes, a fluid temperature system. A fluid system has a fluid pumpand a temperature sensor. The fluid pump and temperature sensor areconfigured to receive a predefined fluid circuit. A controller isconnected to the fluid pump to control a speed thereof and to thetemperature sensor to receive a temperature signal output therefrom. Thetemperature sensor is configured to detect a temperature of fluidcarried by the fluid circuit. The controller operates the pump at atleast two flow rates. For each of the at least two flow rates, thecontroller records first and second temperature data responsive to thetemperature signal at each of the at least two flow rates. Thecontroller calculates an inlet temperature responsively to both thefirst and second temperature data such that the inlet temperature is anestimation of the temperature at a point in the fluid circuit remotefrom the temperature sensor. The calculating compensates for atemperature change in flowing fluid between the point and thetemperature sensor.

Further twenty-second embodiments include ones in which the controllerdisplays the inlet temperature a display of a user interface.

Further twenty-second embodiments include ones in which the calculatingincludes calculating the inlet temperature responsively to an initialestimate of the inlet temperature that is based on the constant heattransfer rate and responsively to an improved inlet temperature estimateresponsively to the initial estimate of the inlet temperature, anestimated or measured of an ambient temperature, and the at least twoflow rates.

Further twenty-second embodiments include ones in which the improvedinlet temperature estimate is responsive to a difference between theestimated or measured ambient temperature and an average of the initialestimate of the inlet temperature and the temperature indicated by thetemperature signal.

According to twenty-third embodiments, the disclosed subject matterincludes, a system for performing a blood treatment. An extracorporealblood treatment device has a controller controlling the extracorporealblood treatment device, the controller is connected to a pump, a sensor,and a user interface. The controller pumps blood from a patient accessthrough a blood circuit to a temperature sensor positioned along theblood circuit remote from the patient access such that heat istransferred between the blood and the external environment of the bloodcircuit as the blood flows from the access to the temperature sensor.The controller pumps blood at a first flow rate F₁ and then subsequentlypumping blood at a second flow rate F₂, records temperatures T_(c1) andT_(c2), respectively, for each of the flow rates, calculates atemperature T_(p) from temperatures T_(c1) and T_(c2) and flows F₁ andF₂, and outputs data responsive to the calculated T_(p).

Further twenty-third embodiments include ones in which the calculatingis independent of a measured temperature of the external environment.

Further twenty-third embodiments include ones in which the calculatinginitially uses an estimated or standard temperature of the externalenvironment but calculates an effective temperature of the externalenvironment.

Further twenty-third embodiments include ones in which the calculatingincludes calculating T_(p) by finding a common intercept of two lines,each is proportional to the same constant heat transfer rate andinversely proportional, respectively, to F₁ and F₂.

Further twenty-third embodiments include ones in which T_(p) iscalculating from: T_(p)=[(T_(c1)*F₁)−(T_(c2)*F₂)]/(F₁−F₂).

Further twenty-third embodiments include ones in which F₁ is a maximumsafe blood flow rate of the extracorporeal blood treatment device.

Further twenty-third embodiments include ones in which F₂ is between 40and 60% of F₁.

Further twenty-third embodiments include ones in which F₂ is between 50%of F₁.

Further twenty-third embodiments include ones in which the controllerrevises the estimate of T_(p) before the outputting includes using aninitial estimate of the temperature of the environment, iterativelysolving for an effective temperature of the environment.

Further twenty-third embodiments include ones in which the estimate ofT_(p) is revised before outputting and includes using an initialestimate of the temperature of the environment to calculate independentheat transfer rates corresponding to each of the conditionscorresponding to T_(c1) and T_(c2).

Further twenty-third embodiments include ones in which the estimate isrevised by iteratively refining the estimate of T_(b) using a singletemperature of the environment.

Further twenty-third embodiments include ones in which the controlleriteratively refines the estimate of T_(b) by estimatingT_(a)=temperature of the environment and solving for a power rate equalto a ratio of a characteristic temperature of the blood at each of F₁and F₂, the characteristic temperature depending on a prior estimate ofT_(p), and using the power rate to calculate an updated estimate ofT_(p) and then repeating with the updated estimate until it converges.

Further twenty-third embodiments include ones in which the power rate isused, at least in part, by calculating T_(p)*=[(T_(c1)*F₁)−(PrT_(c2)*F₂)]/[F₁−(Pr*F₂)], where Pr is the most recent power rate andT_(p)* is a new estimate for T_(p).

Further twenty-third embodiments include ones in which Pr is calculatedat each iteration according to Pr=(T_(b1)−T_(a))/(T_(b2)−T_(a)), whereT_(b1)=(T_(p)+T_(c1))/2, T_(b2)=(T_(p)+T_(c2))/2, and T_(a) is thetemperature of the environment.

Further twenty-third embodiments include ones in which Pr is calculatedat each iteration according to Pr=LMTD (T_(c1), T_(p)*, T_(a))/LMTD(T_(c2), T_(p)*, T_(a)), where LMTD (T_(a), T_(p),T_(a))=(T_(c)−T_(a))−(T_(p)−T_(a))/ln[(T_(c)−T_(a))/(T_(p)−T_(a))].

According to twenty-fourth embodiments, the disclosed subject matterincludes, a system for performing a blood treatment. An extracorporealblood treatment device estimates a temperature T_(p) of the blood of apatient connected to the extracorporeal blood treatment device, theextracorporeal blood treatment device includes a controller thecontroller is connected to a pump, a sensor, and a user interface. Thecontroller is programmed or otherwise configured to implement a method,automatically, that includes: pumping blood from a patient accessthrough a blood circuit to a temperature sensor positioned along theblood circuit remote from the patient access such that heat istransferred between the blood and the external environment of the bloodcircuit as the blood flows from the access to the temperature sensor thepumping blood is effective to convey blood at a first flow rate F₁ andthen subsequently convey blood at a second flow rate F₂. The methodfurther includes recording temperatures T_(c1) and T_(c2), respectively,for each of the flow rates and calculating a temperature T_(p) fromtemperatures T_(c1) and T_(c2) and flows F₁ and F₂. The calculatingimplicitly includes using an effective temperature difference betweenthe blood temperature and an effective temperature of the externalenvironment of the blood circuit for each of the F₁ and F₂.

Further twenty-fourth embodiments include ones in which the effectivetemperature of the environment is a temperature that is calculated basedon the assumption of a uniform temperature of the external environmentof the blood circuit that agrees with the measured temperatures.

Further twenty-fourth embodiments include ones in which the effectivetemperature of the environment is a temperature that is calculated basedon the assumption of a uniform temperature of the external environmentof the blood circuit that agrees with the measured temperatures theeffective temperature of the environment is iteratively calculated.

According to twenty-fifth embodiments, the disclosed subject matterincludes, a blood processing system capable of calculating a bloodreturn temperature. A blood pump is adapted to receive a blood circuitand is connected to a controller that controls the blood pump to pumpblood from a patient at multiple flow rates during a temperaturemeasurement sequence. The controller is connected to receive and storetemperature data indicating blood temperatures in an attached bloodcircuit from a first temperature sensor located remotely from a patientaccess end of the blood circuit, the patient access is connected by anarterial portion of the blood circuit, the temperature data is storedfor each of the multiple flow rates. The controller calculates a heattransfer characteristic of the blood circuit from the patient access tothe first temperature sensor responsively to the multiple flow rates andthe respective temperatures. The controller calculates a returntemperature at a patient access end of a venous portion of the bloodcircuit that returns blood to the patient.

Further twenty-fifth embodiments include ones in which the calculating areturn temperature includes measuring a temperature at a secondtemperature located remote from the patient access and connected by thevenous portion of the blood circuit.

Further twenty-fifth embodiments include ones in which the venous andarterial portions of the blood circuit are parallel channels.

Further twenty-fifth embodiments include ones in which the venous andarterial portions of the blood circuit are parallel tubes over a majorfraction thereof.

Further twenty-fifth embodiments include ones in which temperaturesensor is an active temperature sensor that measures temperature byactively canceling heat flux in a wall of the blood circuit separatingthe temperature sensor from the blood whose temperature is to bemeasured.

Further twenty-fifth embodiments include ones in which the controllercalculates a heat transfer parameter of the blood circuit, the heattransfer parameter is responsive to a thermal resistance of a wall ofthe blood circuit

According to twenty-sixth embodiments, the disclosed subject matterincludes, a system for performing a blood treatment. A blood treatmentmachine is adapted to receive a blood circuit and for pumping blood froma patient. A controller is connected to the blood treatment machine, thecontroller is programmed to pump blood at multiple flow rates during apredetermined operating mode. During the predetermined operating mode,the controller measures blood temperatures, and recording them, so thatthe blood temperatures are measured in the blood circuit at a firsttemperature sensor located remote from a patient access of the bloodcircuit, the patient access is connected by an arterial portion thereofto the temperature sensor, the blood temperatures is measured andrecorded for each of the multiple flow rates. The controller calculatesa heat transfer characteristic of the blood circuit from the patientaccess to the first temperature sensor responsively to the multiple flowrates and the respective temperatures. The controller, responsively tothe heat transfer characteristic, regulates a return temperature at apatient access end of a venous portion of the blood circuit that returnsblood to the patient. Further twenty-sixth embodiments include ones inwhich the regulating is effective to maintain a body temperature of apatient in a predefined range.

Further twenty-sixth embodiments include ones in which the regulatingincludes compensating for heat transfer in the venous portion betweenblood carried thereby and an external environment of the venous portion.

Further twenty-sixth embodiments include ones in which the controller isfurther programmed for detecting a condition indicating that the heattransfer characteristic has changed and, responsively thereto, repeatingthe pumping blood at multiple flow rates and calculating a heat transfercharacteristic responsively to a result of the detecting.

Further twenty-sixth embodiments include ones in which the detecting acondition includes a predefined change in the temperature indicated bythe first temperature sensor.

Further twenty-sixth embodiments include ones in which the detectingincludes detecting a mechanical movement of the blood circuit.

Further twenty-sixth embodiments include ones in which the controller isfurther programmed for detecting a steady state of the heat transfercharacteristic, wherein the recording is responsive to the detecting astead state.

According to twenty-seventh embodiments, the disclosed subject matterincludes, a blood treatment system, capable of calculating a patientblood temperature. An extracorporeal blood processing machine is adaptedfor pumping blood from a patient, a controller controlling theextracorporeal processing machine to pump blood at multiple flow ratesduring a predefined operating mode. The controller measures bloodtemperatures in a blood circuit at a first temperature sensor locatedremote from a patient access of a blood circuit. The patient access isconnected by an arterial portion of the blood circuit to the firsttemperature sensor. The controller measures and records the bloodtemperatures for each of the multiple flow rates. The controllercalculates a heat transfer characteristic of the blood circuit from thepatient access to the first temperature sensor responsively to themultiple flow rates and the respective temperatures. The controller,responsively to the heat transfer characteristic, calculates a patientbody temperature by compensating for heat transfer between the patientaccess and the temperature sensor based on the heat transfercharacteristic.

Further twenty-seventh embodiments include ones in which the heattransfer characteristic is responsive to a heat transfer coefficient anda temperature of an environment of the arterial portion.

Further twenty-seventh embodiments include ones in which the bodytemperature is stored by the controller to a treatment log correspondingto each of multiple patients.

Further twenty-seventh embodiments include ones in which the controlleroutput a signal responsively to a comparison between data in thetreatment log and a temperature resulting from the calculating.

Further twenty-seventh embodiments include ones in which the controllerstores the body temperature to a treatment log corresponding to eachpatient includes a time series of temperatures over an interval of atreatment.

Further twenty-seventh embodiments include ones in which the controlleroutputs a signal responsive to a comparison between data in thetreatment log and a temperature resulting from the calculating.

Further twenty-seventh embodiments include ones in which the controllerrepeats again pumps blood at multiple flow rates and calculates a heattransfer characteristic of the blood circuit in response to the lapse ofa timer.

Further twenty-seventh embodiments include ones in which the controllerrepeats again pumps blood at multiple flow rates and calculates a heattransfer characteristic of the blood circuit in response to the lapse ofa timer initialized at the beginning of a blood treatment.

The embodiments include any method, device, or system of any of theforegoing embodiments wherein any recited calculations are performed bythe controller of a blood processing machine.

In any of the foregoing embodiments in which T_(p) is first calculatingfrom the assumption of a constant heat transfer rate (power units) andthen revised iteratively based on an assumed (or calculated T_(a), theinitial value of T_(p) can, instead, be simply guessed. For example, inthe methods of FIGS. 15A, 15B, and 15C, the step S64′ may be followedinstead of step S64. The value of T_(p) will eventually converge to thesame value. Any of the claims may be modified to guess an initial valueof the recited core temperature, inlet temperature or T_(p) according tohow the temperature is identified in the claim.

It will be appreciated that the modules, processes, systems, andsections described above can be implemented in hardware, hardwareprogrammed by software, software instruction stored on a non-transitorycomputer readable medium or a combination of the above. For example, amethod for calculating human core temperature, blood temperature, ortemperature of fluid in any vessel can be implemented, for example,using a processor configured to execute a sequence of programmedinstructions stored on a non-transitory computer readable medium. Forexample, the processor can include, but not be limited to, a personalcomputer or workstation or other such computing system that includes aprocessor, microprocessor, microcontroller device, or is comprised ofcontrol logic including integrated circuits such as, for example, anApplication Specific Integrated Circuit (ASIC). The instructions can becompiled from source code instructions provided in accordance with aprogramming language such as Java, C++, C#.net or the like. Theinstructions can also comprise code and data objects provided inaccordance with, for example, the Visual Basic™ language, LabVIEW, oranother structured or object-oriented programming language. The sequenceof programmed instructions and data associated therewith can be storedin a non-transitory computer-readable medium such as a computer memoryor storage device which may be any suitable memory apparatus, such as,but not limited to read-only memory (ROM), programmable read-only memory(PROM), electrically erasable programmable read-only memory (EEPROM),random-access memory (RAM), flash memory, disk drive and the like.

Furthermore, the modules, processes, systems, and sections can beimplemented as a single processor or as a distributed processor.Further, it should be appreciated that the steps mentioned above may beperformed on a single or distributed processor (single and/ormulti-core). Also, the processes, modules, and sub-modules described inthe various figures of and for embodiments above may be distributedacross multiple computers or systems or may be co-located in a singleprocessor or system. Exemplary structural embodiment alternativessuitable for implementing the modules, sections, systems, means, orprocesses described herein are provided below.

The modules, processors or systems described above can be implemented asa programmed general purpose computer, an electronic device programmedwith microcode, a hard-wired analog logic circuit, software stored on acomputer-readable medium or signal, an optical computing device, anetworked system of electronic and/or optical devices, a special purposecomputing device, an integrated circuit device, a semiconductor chip,and a software module or object stored on a computer-readable medium orsignal, for example.

Embodiments of the method and system (or their sub-components ormodules), may be implemented on a general-purpose computer, aspecial-purpose computer, a programmed microprocessor or microcontrollerand peripheral integrated circuit element, an ASIC or other integratedcircuit, a digital signal processor, a hardwired electronic or logiccircuit such as a discrete element circuit, a programmed logic circuitsuch as a programmable logic device (PLD), programmable logic array(PLA), field-programmable gate array (FPGA), programmable array logic(PAL) device, or the like. In general, any process capable ofimplementing the functions or steps described herein can be used toimplement embodiments of the method, system, or a computer programproduct (software program stored on a non-transitory computer readablemedium).

Furthermore, embodiments of the disclosed method, system, and computerprogram product may be readily implemented, fully or partially, insoftware using, for example, object or object-oriented softwaredevelopment environments that provide portable source code that can beused on a variety of computer platforms. Alternatively, embodiments ofthe disclosed method, system, and computer program product can beimplemented partially or fully in hardware using, for example, standardlogic circuits or a very-large-scale integration (VLSI) design. Otherhardware or software can be used to implement embodiments depending onthe speed and/or efficiency requirements of the systems, the particularfunction, and/or particular software or hardware system, microprocessor,or microcomputer being utilized. Embodiments of the method, system, andcomputer program product can be implemented in hardware and/or softwareusing any known or later developed systems or structures, devices and/orsoftware by those of ordinary skill in the applicable art from thefunction description provided herein and with a general basic knowledgeof sensor, controller, and/or processor systems and/or computerprogramming arts.

Moreover, embodiments of the disclosed method, system, and computerprogram product can be implemented in software executed on a programmedgeneral purpose computer, a special purpose computer, a microprocessor,or the like.

It is, thus, apparent that there is provided, in accordance with thepresent disclosure, temperature measurement devices, methods, andsystems. Many alternatives, modifications, and variations are enabled bythe present disclosure. Features of the disclosed embodiments can becombined, rearranged, omitted, etc., within the scope of the inventionto produce additional embodiments. Furthermore, certain features may beused without a corresponding use of other features. Accordingly,Applicant intends to embrace all such alternatives, modifications,equivalents, and variations that are within the spirit and scope of thepresent invention.

What is claimed is:
 1. A method of detecting a core temperature of apatient involved in a treatment or diagnostic procedure, comprising:controlling, using an automatic controller, a rate of flow of fluiddrawn from the patient through a fluid circuit, the fluid entering thefluid circuit at a fluid circuit entry at the core temperature, thefluid circuit having a temperature sensor located remote from the fluidcircuit entry with an initial portion of the fluid circuit connectingthe temperature sensor with the fluid circuit entry; the controllingestablishing a first flow rate of the fluid from the patient to thetemperature sensor thereby causing heat to be exchanged between thefluid circuit and fluid; at the first flow rate, measuring and recordinga first at least one temperature using the temperature sensor;controlling, using the automatic controller, the flow of the fluidthrough the fluid circuit to establish a second flow rate, differentfrom the first; repeating the measuring and recording, at the secondflow rate, to record a second at least one temperature using thetemperature sensor; calculating the core temperature using a combinationof both the first and second at least one temperatures; and outputting aresult of said calculating on a user interface.
 2. The method of claim1, wherein the calculating is independent of data indicating atemperature of an ambient environment surrounding the initial portion ofthe fluid circuit by using the first and second temperature measurementsand the first and second flow rates and an assumption of identical heattransfer rates between the ambient environment and the fluid in theinitial portion of the fluid circuit.
 3. The method of claim 1, whereinthe calculating includes solving an equation based on a constant rate ofheat transfer between the initial portion of the fluid circuit and anambient environment.
 4. The method of claim 1, wherein the calculatingincludes deriving the core temperature by initially solving for the coretemperature by solving an equation based on a constant rate of heat gainor loss along the initial portion of the fluid circuit or setting aninitial value of the core temperature to a predefined value.
 5. Themethod of claim 1, wherein the calculating includes calculating a logmean temperature difference based on said core temperature, initiallycalculated based on a constant rate of heat transfer between the initialportion of the fluid circuit and an ambient environment, an estimate ofthe temperature of the ambient environment, and said first and second atleast one temperatures.
 6. The method of claim 1, further comprising:comparing the core temperature to at least one reference temperature andoutputting data to the user interface indicating a condition calculatedfrom the comparing.
 7. The method of claim 6, wherein the condition is apatient fever, and further comprising conditionally outputting anindication on the user interface a signal indicating the patient feverresponsively to the result of the comparing.
 8. The method of claim 1,wherein the controlling to establish the first and second flow ratesincludes measuring a temperature indicated by said temperature sensorwhile holding the rate of flow constant for a period of time effectiveto establish an unchanging temperature indicated by said temperaturesensor.
 9. The method of claim 1, wherein said controlling to establishthe first flow rate and said controlling to establish the second flowrate include flowing at a respective rate for an interval effective toestablish a steady state temperature indicated by said temperaturesensor.
 10. A fluid temperature measurement method, comprising:providing a fluid pump and a temperature sensor, the fluid pump andtemperature sensor being configured to receive a predefined fluidcircuit; providing a controller connected to the fluid pump to control aspeed thereof and to the temperature sensor to receive a temperaturesignal output therefrom; the temperature sensor being configured todetect a temperature of fluid carried by the fluid circuit; using thecontroller, operating the pump at at least two flow rates; for each ofthe at least two flow rates, using the controller, recording first andsecond temperature data responsive to the temperature signal at each ofsaid at least two flow rates; using the controller, calculating an inlettemperature responsively to both the first and second temperature dataand the at least two flow rates such that the inlet temperature is anestimation of the temperature at a point in said fluid circuit remotefrom the temperature sensor and the calculating compensates for atemperature change in flowing fluid between said point and saidtemperature sensor.
 11. The method of claim 10, wherein the calculatingincludes calculating the inlet temperature responsively to an initialestimate of the inlet temperature that is based on a constant heattransfer rate and responsively to an improved inlet temperature estimateresponsively to the initial estimate of the inlet temperature, anestimated or measured of an ambient temperature, and the at least twoflow rates.
 12. The method of claim 11, wherein the improved inlettemperature estimate is responsive to a difference between the estimatedor measured ambient temperature and an average of the initial estimateof the inlet temperature and the temperature indicated by saidtemperature signal.
 13. The method of claim 10, wherein the fluid isspent peritoneal dialysate.
 14. The method of claim 10, wherein thefluid is urine.
 15. A fluid temperature system, comprising: a fluidsystem with a fluid pump and a temperature sensor, the fluid pump andtemperature sensor being configured to receive a predefined fluidcircuit; a controller connected to the fluid pump to control a speedthereof and to the temperature sensor to receive a temperature signaloutput therefrom; the temperature sensor being configured to detect atemperature of fluid carried by the fluid circuit; the controlleroperating the pump at at least two flow rates; for each of the at leasttwo flow rates, the controller recording first and second temperaturedata responsive to the temperature signal at each of said at least twoflow rates; the controller calculating an inlet temperature responsivelyto both the first and second temperature data such that the inlettemperature is an estimation of the temperature at a point in said fluidcircuit remote from the temperature sensor; wherein the calculatingcompensates for a temperature change in flowing fluid between said pointand said temperature sensor.
 16. The system of claim 15, wherein thecontroller displays the inlet temperature a display of a user interface.17. The system of claim 16, wherein the calculating includes calculatingthe inlet temperature responsively to an initial estimate of the inlettemperature that is based on the constant heat transfer rate andresponsively to an improved inlet temperature estimate responsively tothe initial estimate of the inlet temperature, an estimated or measuredof an ambient temperature, and the at least two flow rates.
 18. Thesystem of claim 17, wherein the improved inlet temperature estimate isresponsive to a difference between the estimated or measured ambienttemperature and an average of the initial estimate of the inlettemperature and the temperature indicated by said temperature signal.19. The system of claim 15, wherein the fluid is spent peritonealdialysate.
 20. The system of claim 15, wherein the fluid is urine.